What’s The Law When Home Buyer Or Seller Changes His Mind?

If a home buyer makes an offer on a house,are they bound to it?
If a home seller accepts an offer, can he change his mind?
The Binding Effect of Offers and Acceptances are different for the Buyer & Seller. AND the breach is Time-Line.
(A) Buyer submits offer – Seller not yet accepted offer
(B) Buyer submits offer – Seller accepted offer
(C) Offer Accepted but contingencies not waived
(D) Offer Accepted and contingencies waived