If you (find) a real gold coin near your house, what would you (do) with it?
If you had found a real gold coin near your house, what would you have done with it?
If you (discover) a supernova, what would you (call) it?
If you had discovered a supernova, what would you have called it?
What would (happen) if you (not / wake up) on time today?
What would have happened if you hadn't woken up on time today?