4. Do contracts for the sale of commercial real estate need to be in writing?

Yes, A real estate agreement that consists only of an oral understanding and a handshake will not be enforced by a court.
A contract does not have to very fancy to be valid. If it describes the property and the price, it usually will be enforceable in court.
Obviously, however, it is not a good idea to rely on a bare-bones contract when you purchase commercial real estate.
You need much more detail. At Alert Property Group we use and recommend REIQ standard contracts.