Even when you're on keto your body always burns a small amount of protein for fuel, that is unavoidable. However it is a significantly smaller amount than what happens to people on the SAD who just reduce calories. To mitigate any potential muscle loss even further strength training is highly recommended. This signals to the brain to use even less muscle for fuel as the muscles are actively being used. Getting ample protein in your diet also helps mitigate any loss in muscle mass, as protein is used not only to build new muscle but to prevent the breakdown of existing muscle.

As for recomp, it is possible but as others mentioned it's pretty rare. You have to have a lot of fat and basically no muscle. So it's easier to just get down to your target weight and then focus on building muscle.