This game mostly succeeds at doing what it wants to be - a S3&K-like game. The visuals are very well done, the game probably never breaks Genesis limitations at all, the music is good, even turning the rather annoying prototype Knuckles theme into a slightly nice theme, the controls work properly, the game works as it's supposed to.
However, there are some problems...
-The insta-shield is entirely missing, instead replaced with the drop-dash, not even the one from the S3 Prototype, which makes the otherwise S3&K-feeling game feel... oddly uncanny.
-The first miniboss and boss pretty much lack any sort of danger - the first midboss can be hit even from the side no matter what, essentially turning it into this game's equivalent of the motobug boss from Sonic Chaos (8-bit). The first boss has only one attack and is very easy to hit, making it rather slow and boring.
-The badniks and obstacles in the first zone can't really hurt you much - most of them have small range and can be ignored entirely.
Overall, this is a good game and I'll definitely be waiting for the full version, and the amount of effort that went into making this feel into a legitimate Genesis game is astounding.