While browsing, I came across this ad featuring SMB2J beta footage. Several differences are shown, such as different ground and later levels being earlier (e.g. 3-2 final is 1-2 beta).
Link: https://youtu.be/nvUlOeOZJiQ
Nice find!
>Mario doesn't get the bounce from the enemies.
Some levels must have been vastly rearranged between the proto and the final.
I see
World 8-1 from the first Game
World 1-2 has a Underwater Section
World 5-3 is Different
Is there a Proto Floating around somewhere?
Nice find indeed!
The physics probably hadn't yet changed much from SMB1.
World 8-1 has two poison mushrooms that doesn't seem to have grown from a block, they just appear like regular enemies, although it's hard to tell exactly what's going on. I guess they were added to test or show the new type of mushroom. Also when Mario grabs it, it doesn't seem to disappear like in the final game. It might have been implemented as a normal enemy at first.
The ground was probably changed last minute, as the manual seems to also have that design as well.