Well, I'm not saying anything that people here haven't already said, but your zone was visually beautiful and showcases the "broad and open" school of SBR2 level design level well. Kudos also on the interconnected multiple paths and the use of Spring Hill's BGM. That said, here are my critical observations.
First, why all the Jetty-Syns and Crawla Commanders? The primary purpose of Forest Fortress Zone, looking at the level design, is to run through it as fast as possible. Why risk having the player run into a flying enemy or one of their attacks, killing their momentum as they're forced to stop and possibly fight (and we all know how tedious it is to fend off Jetty-Syns amd Crawla Commanders)? The Crawlas are fine though. If you want some sort of aerial threat so the player doesn't get careless, I'd recommend Gold Buzzes. This is an issue I notice on a lot of custom maps.
I'd also advise getting rid of the sinkhole traps near the end, and especially the one with spikes underneath. I hate gimmicks that punish the player due to unforeseeable hazards. Such level design depends more upon dumb luck than it does authentic skill.
Finally, here's a harmless glitch you may not know about yet...
Sonic jumped out of the right window of the castle containing the seated Crawlas, and is just kind of chilling in mid-air. Sonic can get back into the stage, though I haven't tried jumping through the window on the other side and back yet.
Well, that's that. Good job Kyasarin. I hadn't played SRB2 for about two months, and I'm glad I did tonight.