I don't think the balls are from Sonic 1 'beta', as such - more like they were simply re-used pieces of art. Nothing important, much the same way the enemies were redesigned for Sonic 2 - Robotnik/Eggman's hovercraft, the wasp enemies, and so on.
Well, depends on the "ball" posted in the debug image earlier by Energyck. If you mean the "giant" ones, those are simply the transporter/shooter in Oil Ocean Zone that can even be found in the final Hidden Palace Zone (if you know the legitimate way like me or if you use a savestate). The second, smaller ball on that platform can be found in the final as well as in Hidden Palace Zone final (albeit garbled graphics) as well as the switch for it. Of course, anyone who has taken the time to look already knows this and I've just wasted my time with all that... But on another note, Sonic 2 is like any game and by that extension, movies as well. The final product rarely resembles the first idea for the game/movie. The large green balls (transporters/shooter) do look like a modified palette from Sonic 1's brown ball weapon for the boss of GHZ.
The wasp enemies are almost completely the same to S1 in code; just a speed difference. So I have reason to believe that S2 Wap was based of S1 Buzz Bomber And if anything is that giant ball from S1, it's the beta OOZ swtich one. :P EDIT: Green balls have different shading types. The beta OOZ switch ball's shading is more similar.
They are not found in Hidden Palace, the debug menu among other things were somehow "OOZed up". I don't know why they'd edit Sonic 1 ball art to make shooters like that. o.o
Also don't forget that Sonic Team use ideas that they have or steal again and again and again. Like the HPZ bridge being used in S3's ICZ, for a minature example.
Note the bold and italic text in the quoted quote. EDIT: Of course, it would be handy if I included bold and italic text. D'oh! :P
I just played S3's ICZ, and I don't see much resemblence to HPZ's bridge. Im interested... what else did they re-use?
The glowing bridge is basically reused from HPZ in the beta. I can't remember other similarities, since it was like last september that I started picking up on them and I've not really played Sonic since.