The Superior Alternative: Sonic 3 A.I.R. (Angel Island Revisited)
If you didn't buy the original classic collection before 2022, you cannot officially "download the ROM" directly from Steam anymore. Your primary legal options are:
Steam is a digital distribution platform developed by Valve Corporation, primarily used for purchasing and playing PC games. While Steam does offer a vast library of games, not all titles are available for purchase or download, especially when it comes to classic games like Sonic 3 and Knuckles.
: A powerful, free emulation frontend that can load your legally extracted Steam ROM using the Genesis Plus GX core. To help you get the best setup, let me know: