You need to upload a legitimate Sonic 2 ROM. (REV01)
You can get this by buying the game on Steam.
After that, it should be at one of these locations:
Windows: C:\Program Files (x86)\Steam\steamapps\common\Sega Classics\uncompressed ROMs\SONIC2_W.68K
macOS: ~/Library/Application Support/Steam/steamapps/common/Sega Classics/uncompressed ROMs/SONIC2_W.68K
Linux: ~/.steam/steam/steamapps/common/Sega Classics/uncompressed ROMs/SONIC2_W.68K
You can get this by buying the game on Steam.
After that, it should be at one of these locations:
Windows: C:\Program Files (x86)\Steam\steamapps\common\Sega Classics\uncompressed ROMs\SONIC2_W.68K
macOS: ~/Library/Application Support/Steam/steamapps/common/Sega Classics/uncompressed ROMs/SONIC2_W.68K
Linux: ~/.steam/steam/steamapps/common/Sega Classics/uncompressed ROMs/SONIC2_W.68K