Asbestos, even if in the tile or glue (most likely glue), will not be a problem for you. Just don't grind/sand them, releasing the fibers.
There is no good answer. Loose tiles can not be located and there is no answer that removing a small area will give you a permanent solution. If one tile was loose, probably all surrounding tiles. You can try grind/cut off 12x12" section of the leveler, razor/chisel out the tile and level over, but all tiles will be loose. Are you using floating floor? Then maybe best if you ignore it and floor over.
There is no good answer. Loose tiles can not be located and there is no answer that removing a small area will give you a permanent solution. If one tile was loose, probably all surrounding tiles. You can try grind/cut off 12x12" section of the leveler, razor/chisel out the tile and level over, but all tiles will be loose. Are you using floating floor? Then maybe best if you ignore it and floor over.