Yeah he mentioned Angel island in particular was because the Ruby made it fall IIRC. I know it was also said somewhere that some of the levels were affected by the Ruby and some weren't. Now that we have some understanding of how the Phantom Ruby works from Forces (though it's not exactly consistent) I'm guessing Green Hill, Chemical Plant, and possibly Studiopolis are virtual reality, as well as Stardust Speedway. I'm gonna go ahead and assume everything afterwards is real. That takes care of the SS to HC transition, with SS disappearing and them falling into the real HC since they've been on Angel island the whole time. They'd then take the Tornado (left in Angel Island at the beginning of the game) to Mirage Saloon, and Oil Ocean is a different one from Sonic 2, just another oil rig built by Eggman. The Little Planet is either warped there by the Ruby (somehow) or is just passing by Earth again like in Sonic 4.