At the SCARZ forums, there was a topic about old ads from the Sega / Nintendo console wars. In that thread, a page got posted with lots of old TV ads in for Megadrive / Genesis games, among others. The Sonic 2 ad intrigued me, as it contained footage from a version that I for one hadn't seen before:
There's a lot of evidence in the video pointing to the fact that this is taken from a much later prototype of Sonic 2:
1. The Title Screen
Similar to (if not the same as) the title screen pictured in the Sonic 2 Manual, which I believe may also have come from this version. It's the same as the dumped proto, but with the 1 PLAYER and 2 PLAYER options at the bottom, in orange and white (coloured similarly to how Esrael recreated it in earlier versions of his Delta hack). There is evidence that this menu was probably functional, as the text reading 1 PLAYER changes between orange and white the first time you see it.
2. The Sonic Sprites
It's hard to see, but it looks like Sonic has his final Sonic 2 sprites in this proto, as in shots from other later prototypes.
3. Zone Graphics
Chemical Plant still has the same loops as in the dumped proto, with the sloping corners... (That weird garbled block is actually Tails flying BTW, it's just the low quality of the vid. Interesting to note that he can fly in this version, though).
However, Casino Night now has the same graphics set used in the final.
4. Special Stage
Is active. Not very important really, but I thought it worth mentioning since I haven't seen any shots of the Special Stages inamongst any proto shots I've seen.
As you'd expect from a proto this late (having seen the pics of Sonic and Tails spindashing with dust trails in the proto Casino Night, I mean), the Spindash has the dust trails.
Also, an interesting glitch I found in this vid:
Tails' tails coming loose when fired from those cannon things in Oil Ocean. XD Just thought that one was worth noting.
Anyway, just thought that was a bit interesting. Like I said, I apologise if this is well-known. ^_^;