This has so much potential! I really like Sonic's physics and the way he controls. In a lot of the recent Sonic games from the past 15 years or so, like Forces and Colors, he feels too heavy/clunky and you don't have very good control over his movement, and the platforming has to be simplified in order to compensate for that. But his gameplay in this demo is pretty much exactly how I expect 3D Sonic to feel. He's fast without being out of control, and he has a nice floaty jump like in the Adventure games. I could see some really fun levels being built around this gameplay. I also appreciate the incorporation of the bounce, it's a really underrated game mechanic that I wish Sega would bring back. And it even runs really well on my 7 year old laptop which wasn't good for gaming even when it was new, lol. I really hope you keep working on this project!
PLEASE DO NOT GIVE UP ON THIS. There is SO much potential here. I can tell a lot of the jankiness of the game is just something that needs to be ironed out over time - like controls, collision, camera, level design, etc. And it wasn't even that bad. But I have ONE big suggestion.
ADD A ROLL BUTTON!
Is this the Bumper Engine? It feels like it is - and even if it's not, you should still add a roll button. You clearly understand how going down slopes and gaining speed is a big part of Sonic - and thats what I had the most fun with in the level. But it was awkward to initiate this high speed state as I had to stop and spindash in order to get it started. A roll button, preferably mapped to one of the bumpers of the controller, would help this game rise HIGH! A button that sends you into a curled state and keeps you in this state as long as you're moving forward. Keep doing what you're doing here and ironing everything out. There is so much potential here.