Right from the start you'll notice two things: 1. The music in this zone is from Star Light (Like on Nick Arcade), and 2. Tails is missing (Also, like Nick Arcade). If this WERE the Nick Arcade build, the explanation for the latter would be because if Tails would get hit the contestant would lose all their rings, making the contest somewhat rigged.
Final
Beta
Act 1 contains quite a few noticeable layout differences between the Wai beta/Final:
Act 2:
Final
Beta
Act 2 is pretty much the same as in the later versions, save for some minor changes as you approach the middle
Like always, Robotnik appears at the end of this act, and does his usual stuff.
However, unlike the other beta, he explodes, rather than just falls apart. However this is due the remnants of Sonic 1 still in this game, as the explosion effects are not that of Sonic 2:
 Sonic 1 |
 Sonic 2 Pre-Beta |
 Sonic 2 Final |