: Sega has delisted the standalone Sonic 3 & Knuckles from Steam to encourage sales of Sonic Origins. This has made the specific .bin file harder to acquire legally for new users.
Switch Online subscribers can play the Genesis versions of Sonic 3 and Sonic & Knuckles with lock-on fully implemented. Sonic Knuckles Wsonic3.bin File Download - Google
If you already own the game on Steam, you do not need to download it from an external source. You can find it in your local files: : Sega has delisted the standalone Sonic 3
The game also features a unique "Lock-On" technology, which allows players to access special stages and game modes by using a special cartridge. If you already own the game on Steam,
: Sonic 3 A.I.R. requires this specific ROM to verify legal ownership and to load original game assets (graphics, levels, and logic).