In WA, if the agent found the buyer, even without a contract, they’ve done the work and are entitled to commission. But yes they’d have to sue you for it if you screw them over. Then it’s commission plus damages. Good luck. All decent brokerages have law divisions.
Uh, you totally can. Even if you signed a contract few agents would action it and they're only entitled to a percentage that you would probably have to negotiate after mediation or litigation. It would make you a greedy sack though, and your buyer would walk if they were smart. You stink.