4. He put a deposit down for a car but then has second thoughts. Can he withdraw from the deal and ask for a refund of his deposit?
It is likely that Mr. B will lose his deposit. He has broken his contract with the seller, and the seller is entitled to compensation.
If Mr. B is asked to put down a deposit (but he is hesitated to confirm the order), he may ask whether or not the deposit is refundable. He may then request the seller to put that down in writing in order to avoid future arguments.