Ok, I'll try not to be harsh with this since I understand you're a beginner, but here's some stuff I think you should improve:
Length: Levels in SRB2 are about 3-5 minutes in length, aim for that level length.
Level Design: For a "Modern Sonic required" map this does not look like Modern Sonic level design. There is an over-reliance of Light Speed Dash Ring trails so that the level can justify being a Modern Sonic exclusive stage. I also feel like the level design is way too open ended for Modern Sonic. Make it more linear, but make some pathways here and there.
Secrets: Secrets should be hidden more cleverly, as the only secret present in this level is hidden very poorly. I recommend hiding said secrets in pathways that are harder to reach than the normal path.
It's not all bad though, I like the general level aesthetic, I think the cave section is a really cool idea, reminds me of Green Hill Act 2 of Sonic Generations, and there is clearly a lot of effort involved, I also tried to make a "Modern Sonic exclusive stage" but it didn't turn out too well, so I commmend you trying this idea out! I just think it could've been executed a bit better.