Developer of Sonic Before/After the Sequel actually did that, Spark the Electric Jester. First game is classic Sonic meets Kirby while second and third are Sonic Adventure inspired.

Fuck the Labyrinth Zone. Fuck the Aquatic Ruin Zone too, it’s not even that they are hard, they are just so slow and unfun. With Aquatic you can try to avoid by staying up top but I always fall to water fairly quickly.