How to make 3D levels

How do I make 3D levels like in Sonic 2?

You can’t. I have a FNAF game that’s sort of like 3D, but is just a game mechanic messing with size etc.
Mhx air had an interesting concept about a 2d map that affects the 3d movement:
Here’s my “3d”:

The special stage in Sonic 2 wasn’t 3D, it was faux 3D like Pole Position. You just need a background object with about 100 animation frames that looks like a moving road, and rings that spawn in areas and change size from small to large. When the rings are small, make an off switch for collision, and when they are full size, have the switch turn on, so collision adds a ring and destroys, or it destroys right after being full size, if you aren’t standing where the rings spawn. This makes it appear as if you are collecting rings when you are close enough. For Sonic, a walking forward animation loops, and pressing left and right move you left and right, but with rotations for the roundness of the shape, and you rotate in a complete circle. I’m sure you could just attach a sonic sprite to a big circle that rotates, that would be easier, probably.

OK thx