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.
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.