They mostly did work on Amigas.
Also, to people asking about various Sonic 2 builds.
I know of several unreleased Sonic 2 builds that exist physically. E.g. there is a post-NA build with MCZ in it, and a more complete HTZ. There's also a very late alpha out there (almost beta). Etc. Usually when I mention these people say 'Man, Sonic 2 is boring, bring us Sonic 1/3 prototypes!'
People suck. I'd love more Sonic 2 prototypes =D
Are they even possible to obtain or has that ship sailed?
Indeed, both of these sound very interesting. = ) If either of these is in a position to be obtained, I'd totally donate some cash to HPZ to go toward their acquisition.
Also, to the people suggesting Neo Green Hill Zone to be intended as a possible Emerald Hill Zone name rather than Aquatic Ruin Zone, remember that as shown in the SEGA Solid Gold Guide, Aquatic Ruin definitely had a title card reading "Neo Green Hill Zone" at one point. I know we've established that the Level Select text cannot be trusted as an accurate source due to it not being updated in several instances, but since the title card and level select text are unrelated surely they wouldn't bother to implement a title card that used a name not intended for the Zone in question? After all, QA Beta 4's title cards do not correspond to the level select in the case of MCZ, ARZ and WFZ, since they have earlier / incorrect names listed in the level select which were ignored when creating the title cards.
That said, I guess the only way to be sure would be to acquire a prototype between the Wai prototype and QA Beta 4 - if, for example, Mystic Cave had a title card reading "Dust Hill Zone" in such a build, then it'd certainly lend credence to the theory that the name "Neo Green Hill Zone" was not intended for Aquatic Ruin: in light of the new information from Yasuhara regarding Dust Hill Zone, it would show that they had implemented another Zone's title card using an incorrect name, meaning the same situation could have occurred with EHZ and ARZ.
Apologies if I'm being an idiot - don't hesitate to point out any flaws in my reasoning. After all, we all live and learn. = )
BTW, mad props to the people who contacted Yasuhara and got the info about Dust Hill Zone being the intended name for the desert Zone.