you can submit, but can not win a compo with a SNES game, which just runs from the GB cart. because it is a Game Boy compo, not SNES. judges will run entries on the real hardware: DMG, CGB and emulators: BGB or SameBoy.
rules say:
4. SGB features are allowed. The entries will be evaluated mainly on Game Boy (Color). You can use SGB features, but don't rely on them as main features for your entry.