Who at fault if A and B were right next to each other going straight in a parking lot and B brakes it and turns almost complety around and hits A in the driversid door And what if he has no insurance?

The way you are describing it B is At Fault. If B is at fault and has no insurance, A's uninsured motorist coverage will take over as if the person had coverage. Any amount paid out will be retrievable by the insurance company through suit or other means. You subrogate your loss to your insurance company so that they can go after the other party for damages paid.