>>14456553hurrrrrrrrrr durrr
you managed to kill my mega mewtwo now you have to fight mega medicham.o you managed to kill that i will blizzard spam you to death with mega abomasnow.
thats a YES to one per battle question.
and
a big NO all six pokemon are megas.
you know what would be cool if you unlocked more mega stone slot than one every time you manage to beat the elite four and they continue to get extremely harder and luckier in terms of accuracy and pokemon get stronger or replaced with harder pokemon every time you beat the elite four.(only for single player use not unlimited mega for online battles.)it would really make you earn those stones.