I don't think I have an adequate title for this issue but oh well...
Sonic 3 A.I.R. is now available and, according to the site, I have to install the Steam version of Sonic 3 & Knuckles (for game files). However, I own it as part of the SEGA Mega Drive and Genesis Classics bundle, I don't own it individually. Steam doesn't give me the option to download it as an individual game. Clicking Play on the site launches the game through SMD&GC, not as an individual game. How do I do that so I can play A.I.R.?