Is there any difference between an ankle strain and dislocation?

Yes: A strain is a pulling of the ankle ligaments. A dislocation usually involves tearing of the supportive ligaments and the talus being pulled out from between the tibia and fibula.

Yes: A sprain involves stretched or sore liagment(s). A sprain involves the muscle or tendon. A dislocation is when the joint has fallen out of alignment and no longer functioning anatomically correctly. This is normally worse than a strain, or sprain and needs to be relocated.