Can you put a 12' x 12' above ground pool in the basement?

Physically, yes, if it will fit in the room and the floor will support it. Local codes may not allow this and a person in the pool might be dangerously close to the ceiling/floor joists. An equally significant issue is that the pool will create a great deal of moisture that can destroy the house from mold, mildew, plaster decay, and wood rot. (and how do you drain the pool... ?)