I think that all levels should be possible with the SB1 moveset, but It might be much harder and I just haven't realized because I basically mastered the game mostly. (game didn't have play testing from people other than me)
And the lack of rotting enemies is a miss on my part honestly, I didn't add them beause of time and then forgot to add them back. I think i might add them back on an update soon.
Anyways, I'm glad you like it!