It looks like it won’t fit a GameCube since it’s attachable to the sides of the Switch like a joycon.

Nintendo is generally only backwards-compatible by one generation (example: Wii can play GameCube games but not N64 games), but there’s at least three remastered games in Super Mario All-Stars that are from older generations.

If you have a Switch emulator (I have no idea where to find that), it might work on a PC.