Although it's simple, at least it can be improved (Sorry if I'm being picky)
Move set: Please put the stomp on the Spin (it's easier to press), the Homing Attack could be a little more free (holding Jump), it would be cool if we could do the Spin Dash manually (the manual Spin Dash is suggestion) It would be better if the Boost was separate from the energy blast (and the Boost in Custom 1), the ability to fly could be placed in Custom 3 (and the energy blast in Custom 2), and Sonic would be Too fast, with the Boost being difficult to control.
Sprites: Add some things for compatibility, like the sprite on the rails or falling on the ground (X Momentum). Improve it over time (it's kind of ugly, but acceptable as it's your first mod), and ask for help to the spriters, since they have a lot of experience.