Well, this is fun.
Layouts are very solid, flow well, and are generally fun to play through. The new music and miscellaneous graphics are refreshing, as is the idea of an options zone. However, the options themselves are extremely redundant for the most part; I don't really see a reason to warrant a whole zone for them. The character select is a nice touch, though. The alternate difficulties are also rather interesting, though I don't personally see much of a need unless the layouts are completely different.
I absolutely despise your method of accessing the main special stages. The special rings gimmick was horrible and annoying in Sonic Advance 2, and that notion is no different here. As a result, I don't think I'll ever be able to check out Hyper Sonic—which sucks rather hard, because I wanted to see how he was different. I do, however, appreciate the save feature, though I can't help but feel the number of menus is a bit ridiculous.
The sound choices are rather basic, but not detracting; they're not brilliant, but they do their job, fitting the zones quite well.
All in all, I'd say this is a pretty solid hack. Nice balance of changes, not incredibly difficult, and it includes a wide array of features which can increase playability to a large degree. Nice work, and I hope to see more from you in the future!