If you didn't purchase it before it was removed, you typically need the ROM file to use popular fan projects like Sonic 3 A.I.R. (Angel Island Revisited) Where to Find the ROM
Sonic 3 and Knuckles is a classic platformer game developed by Sega, released in 1994 for the Sega Genesis. The game is a sequel to Sonic the Hedgehog 2 and follows Sonic and his friends as they try to stop Dr. Eggman's evil plans. Sonic 3 And Knuckles Steam Rom Download Free
The software looks for the Sonic_Knuckles_wSonic3.bin file in your Steam directory. If you didn't purchase it before it was
Sonic 3 A.I.R. is a fan-made "remaster" that runs natively on Windows, Mac, and Android. It adds 16:9 widescreen support, 60 FPS gameplay, bug fixes, and a massive modding community. However, to prevent legal issues, the developers of A.I.R. require you to provide your own (from the now-delisted Steam version) to run the game. Staying Safe: A Word on "Free Downloads" Eggman's evil plans
Since it cannot be bought directly on Steam anymore, you must use other legal methods to obtain the ROM file: