Sonic 2 And Time

I think it's pretty safe to assume that Sonic 2 was originally planned to sue the Time Travel format in Sonic CD, or at least a version of it. However it seems that the format was to be used in a different way, as far as I can see.

Wood Zone is obviously the Past of Metropolis City (it has the same kind of archways in the tree logs, like the lifts, and has convyor belt type apparatus like in Metroplis City), Dust Hill was rumore to be the Past of Emerald Hill (I think) and Genocide City was the Future of Chemical Plant. Assuming for a second that Sonic 2 was going to use Time Travel, why do only a few Zones actually have different Time Periods? And why are so many of them from the Past? Could Sonic have moved from Present to Past and back to the Present again? If so, why weren't thee any Future Levels? Or maybe there were Future Levels and they weren't all made. Maybe each Level was to have Three Acts; Past, Present and Future? (Slight evidence of this comes from the Three Act Metropolis City Zone in the final Sonic 2) Perhaps Sonic didn't transverse every Zone in the order of Past, Present and Future? (Slight evidence of this comes from the Sonic 2 Beta where Sonic Vs Eggman in the Emerald Hill Zone (Present))

It's a shame there isn't a more complete ROM of Sonic 2 Beta to test the whole Time Travel theory out. It seems Sega like to have lots of plot holes in their Sonic games which they never explain (like the evidence of the Spin Dash in Sonic 1, the never quiet fully explained Sonic Crackers/Espio's Chaotix, the missing level in Sonic CD and the Time Travel element of Sonic 2)

And just what is that "master Emerald" there for in Hidden Palace S2Beta? :?