You are essentially looking at a complex waiting list situation.
Deposit at #3.
If #1 comes through with the money, deposit there. Then thank #3 very profusely and tell them that your plans have changed, and let them know that you won’t attend.
If #1 doesn’t come through with the money, and you have a chance to check out #2 and decide you do like it better than #3, then deposit at #2, and follow up with the profuse thanks and plans have changed steps with #3.