Concordian Coast Zone by Ktoby & Pronicthewedgehog
This seems to be your first level, and it really shows. However, that's by no means a bad thing! Concordian Coast is a very charming experience and I can see you two put a lot of love in making it memorable through all the details it had. Beginners are usually discouraged from joining the OLDC due to the competition, but the feedback you can gather from it is just as important: stick around and you'll be making amazing maps in no time.
Tip: checking the Extra flag (labeled as Float in Zone Builder) will automatically make rings float above the floor.
Toffee Tor Zone, Act 1 by RoyKirbs
From all the progress you shared about this level I was really excited to interact with the rollout rocks in a fun and original way, but in my first playthrough for some reason I managed to accidentally avoid every single one of those sections and mostly safely tread along the rooftops to the point I was even wondering if I was actually playing the level you teased, and only actually knew there were rollout rocks from other people that played. I'm not sure to what to attribute that to but I might have to do a double take with other characters to see if the experience is the same for all of them. Meanwhile, I feel that it's important to point out: not every section of your level has to be a path split or multiple paths: it's okay to have mandatory bottlenecks everyone has to go through, which is something I think Enby Echoes excelled at having.
Metallic Madness Good Future by Kwiin & Kanna
Everyone's been praising this level and for good measure: it's dressed to impress, and the momentum mod is sure a powerful addition... if it worked for every character. The lack of meaningful hazards and springs made me feel like I was enjoying a peaceful walk in the park, but not much more than that. And well, that's what Good Future Metallic Madness is after all, and there were some interesting platforming sections at the start too, but what the level was probably aiming for was the feeling of breezing through the open spaces and that's something I don't think I was let achieve.
Wasteland Wilds Zone by SunCyclone
This one seems to be the first, or one of the first of your levels, and I really gotta praise you for the good job! The pacing is steady, the theming is consistent, and there's all sorts of goodies to find if you go out of your way. The major shortcoming about this level however is just how open and empty it looks: it lacks decor, and sometimes it isn't immediately clear where you should go. I figure this is something you'll get the hang of if you spend more time on each area figuring out how to make use of your empty spaces, but for now you should definitely give yourself a pat on the back.
Wild West Zone, Act 2 by Dead
I don't think there's anything I dislike about this one: you've tried to tell a story, one that required a very satisfying spin on the canyon theme, from the environment to the music. The visuals are absolutely stunning: the level is reasonably sized but no part of it feels empty, cluttered or unattended to, and that attention to detail definitely sold it to me. It felt a tad short due to the path I might have taken, but the most memorable part of it to me was that the button-pushing parts weren't brainless as much of button-pushing parts usually are and actually made you move and confront enemies before the buttons actually did something, and at the very least I think that's a very interesting addition to the environmental storytelling of the stage. This is a strong competitor, so keep up the amazing job!
Rustic Templar Zone by MK.exe
From the level of attention given to character paths, visuals, flow, and all the baggage you have with levels that are indeed fun to play, it's not like you don't have competition, but I think it's finally the time you snatch the Contest Winner title you deserve. No complaints.
Shadow of Atlantis Zone by akirahedgehog
This level captured my attention from the moment I saw it submitted: the visuals stemming from your own interpretation of what Shadow of Atlantis for the 32X should be are definitely captivating. However, how well this stage translates into something enjoyable for SRB2 is a bit questionable because it doesn't know what it's trying to be: it is very wide and there's a lot to see and discover, but it's all mashed together into something confusing. I pushed some buttons that had no immediate effect on the surroundings, and if they did I could not tell their use for progress, some doors remained locked despite everything and it was never clear where I should go, and to top it off, most of the stage is underwater and bubbles are very sparse, which cuts half if not all of the will someone would have of exploring it to the fullest. When I finally came to the ending, I felt like there was a whole undiscovered world I left behind, and that left me wanting more even though I couldn't bring myself to try again. This is why I think there's potential to this map: with some polish and a little bit more of focus, it can become something stellar. I hope you're willing to work on it further!
Oasis Palace Zone by So2ro
Where this map really fails to impress is that most of the rooms look largely the same and it never felt like I was progressing at all: enter room, find dust devil, then launch myself to the next room. Were there more landmarks in each room that made it clear that "ah, this is a new place I haven't been to, nice" and the challenges with the dust devils actually escalated, this level could play much more interestingly, but it falls a little bit short.
Heroes Hall by Zaxel
Your levels definitely have improved a whole lot since your first releases, so it's really satisfying to watch your progress. I can't say much about this level other than a problem that's been consistent through most of them: there is just too much level. They are too long, either because there's too many intermission rooms that could be easily axed out, or because there's too much mandatory content: cue the Heroes Hall. While it's very interesting in concept, finding buttons to progress gets stale when there's 6 or 7 of them and some are hidden in nooks in walls or after a maze (please don't put actual mazes in your levels, let alone under Robo-Hood attack and low brightness). The level could have benefitted from splitting some of the Heroes' rooms into different paths so you didn't need to go through all of them in a single run, and then have a nifty unlockable for completing every Hero's for persistent players, as well as custom scripted challenges for each Hero that aren't mere button pushing: the possibilities are limitless. You have a lot of potential, so keep going!
(Also make sure the scripts you bundle in your level don't change a player's control bindings for good. You were definitely saved this time)
Cyan Heights Zone by PencilVoid
Despite a rain of criticism over how cramped your map looked along its development, you didn't give a shit and hit the gas anyway. And that's okay! If you're not having fun with what you're doing you might as well leave, right? I do want to point out though that steady footholds are a must for Sonic levels because if there you're not sure you're going to land safely you're not going to tread comfortably and the whole level will not feel good as a result. All in all it felt very short and I happened to find the end of it accidentally, so it didn't leave anything for me to comment on - if you're aiming to impress and bring something fun to the table, Cold Zone is something to go for instead.
Anteggtica Zone by Radicalicious
There were no rings in this map. Rings are essential for Sonic's survival, so they are usually placed in large quantities across levels in every Sonic game. They defend Sonic against hazards, but that's in the case there are hazards to be wary of, that the map also didn't have, save for 4 BASHes that were mostly unthreatening. The level layout was definitely there, which is why I trust you can make something that's fun to play, but I believe this one could have stayed in the backburner for a bit longer.
Aqua Paradise Zone by Twins'R'Awesome
Aside from the technical difficulties, this level is a sight to behold for sure, even through the textures were not always appropriate to where they were applied to. It had a lot of springs, which were fun to bounce around and breeze through the level with, but that was mostly it. The upper (non-underwater?) path started to become repetitive and feel blocky, and when I finally got to experience the first outdoor sections with the rocky structures and thought "wow, now this is where it really starts" it didn't start and I was in an indoor section again with the same spring gauntlets and lacking decor. It's definitely something to expand on, however, so keep at it.
Hypertower Zone by WasifBoomz
It's cool to break away from the standard GFZ-like greenery for a first level (assuming this is your first) and go crazy with different concepts but this one looks like it wants to be a challenge level so bad even though it lacks some of the understanding of what makes a level challenging, and unfortunately it isn't fun to wade through as a consequence. I'm not sure myself of what could be done to salvage it, but I know you can make something even more interesting if you start from scratch.
Valley Falls Zone by Hamsandwich
This may be your first level and while I was willing to give it a chance it just threw a wrench in my hopes and dreams with the underwater maze. Mazes are not fun, specially when they don't have an indication of where to go and you will die if you don't stop looking for the exit to be able to breathe, and if the algae were supposed to be hints, they didn't work. I didn't finish the level because of that, and up to then it was somewhat enjoyable, but it left a permanent sour aftertaste regardless. I'm not ranking it explicitly low because it was a heartfelt attempt to make something enjoyable, but please keep the advice for next time.
Hectic Harbor Zone by ACStriker
Replaying this level as Sonic actually made me remember Sol Sestancia's level design, in a pleasant way: I certainly think there's potential if you had more time to plan your maps out. I have no major complaints about it since it's fairly level-headed, but it would be nice to see you trying something more fleshed-out and polished for next contest.
Myriad Memories Zone by ManimiFire
While this stage is interesting in concept, the challenges felt short and unfocused: out of the blue there's a memory trial? I appreciate that you made the platforming one non-lethal, but the Modern pulleys are uncomfortable to use and to platform with, and ended up looking out of place within the dungeon-like areas. I feel like this could be explored more with challenges that are more consistent with themselves, escalate properly, don't involve pushing gargoyles and above everything, don't use sector darkness as an artificial challenge. It doesn't matter if you intended to do that or not: it unfortunately detracts from the experience altogether.
Overgrown Heights Zone by InferNOr
Aside from the inconsistent framerate I was getting for whatever reason, this level trades dangerously on the line between difficult and unfair. It sure is beautiful and very creatively themed and decorated, and I'm definitely ranking it decently because of that, but some parts of it felt like I was being played pranks on. Some jumps are too tight; platforms up a waterfall were sloped, preventing accurate jumping; an out of view Canarivore snipes you from over a branch hanging above a death pit; some star posts were so poorly placed it almost felt like they were hidden, among other minor quirks. It's probably a matter of polish, though, so my recommendation for this one is to have your level playtested by someone for difficulty: your level will always seem easier to you. Be merciful towards players, and don't assume much: always have some sort of leeway.
Crystal Cave Zone by CST1229
This seems to be your first level, so what I can offer as advice is to be more mindful of your geometry towards the textures you choose. You picked colored tiles as a main texture, but them applied them to irregularly angled walls and without watching if they actually tiled, so in large quantities they clashed with every other objects and looked uncomfortable as a result. When playing with square tiles, it's a good idea to make everything straight angled, raising some sectors here and there to make for an interesting cave-like setting. Other than that, the was also quite cramped and short, and even though this is a common first mistake, I'm sure you'll get comfortable with more open areas if you keep trying. This level also lacks FOFs altogether where it could pretty much have them so it seems to me that you haven't tried including them: it is difficult to make an interesting level without making use of floating platforms so I should suggest going over the tutorials. They're very simple to make, can enhance your level greatly and you'll get the hang of them in no time.
Cluttered Cave Zone, Act 2 by Riolucariolu
I'm unsure of theme you were trying to go for here, since the level started with a wet cave, and then became kind of crystalline, then a temple... and then lava... and for some reason you've offered to the player a pair of shields that can trivialize the second half of the map completely, which sort of tells me you weren't that confident in what you were making in any part of the design process. You sure have the potential to make something really great, but the first part of making a map is to conceptualize it and a lot of people underestimate that. Put what you want to make on a paper and revise it until you get something you'd like to see, and then get prepared to revise it again a lot. Additionally, your starposts weren't properly set up, so all of them counted as the same, but my actual complaint about your level is that the exit was literally hidden - the red spring that takes you there is simply not in view and there's little indication that it's even there. Never make the player stop dead in their tracks wondering about what to do or where to go: always provide them a way to at least view or preview their next step.
Magma Falls Zone by RadicalChaos_6922
Unfortunately, this feels like an unfinished product. You can tell because technical prowess definitely isn't lacking: there's a lot of care put into decor and topology (so much that there are so many linedefs the game can lag from it) but everything else is just inexplicably wrong. 90% of the level is comprised of the same texture, all misaligned; some fans did not match the radii they were visually supposed to have, and were not accompanied by particle generators to indicate their maximum height; there are way too many hills that invite you to laboriously climb them jump after jump as if they hid something but are merely a waste of time with nothing on them, which can discourage a player from exploring your level altogether; the level itself is branched convolutedly in a way that wraps around and can get you lost easily, since there are little landmarks, along with an out-of-place teleport and the fact that it completely lacks starposts; a set of springs are placed next to a ledge that's too high for them to reach even with a power springing Amy; speed bumps along the first lava pool to prevent you from going fast on the rollout rock for no apparent reason, and so on. All of these mistakes and poor choices could be easily spotted by someone remotely competent playtesting the level, which leads me to believe it was not, and so I'm abstaining from commenting on its quality, but I hope the OLDC experience can at least give you the advice you need.