Genesis's Sonic 2 3D Classic is an emulator, I know that for sure. I think, even if they claim they're ports, they're emulation. There's an injection tutorial on a 3DS iso site.The 3D classics aren't emulated though. They're ports.
While you're here, could you build the NXEngine port of Retroarch on either a newer or older (1.0.0.1) version of Retroarch? 1.0.0.2 has some game breaking glitches that make you unable to progress in the game.