Xerneas does not have a Mega Evolution.
mega drain in Pokemon is a grass type move that works better leech seed or leech life
Mewtwo can Mega Evolve into either Mega Mewtwo Y or Mega Mewtwo X.
in a route
No.
In Pokemon X and Y you are not allowed to sell mega stones unfortunately. They are considered a special item.
5-6 gb
Yes, the Mega Gyrarados is a flying Pokemon and a water Pokemon.
Xerneas does not have a Mega Evolution.
Mega Rayquaza
My good sir, mega balls are nonexistent in the pokemon video game series.
No, because Mega Evolution wasn't introduced until Pokemon X and Y.
Have it hold the Sceptilite, then press "Mega Evolution" during a battle to Mega Evolve it.
mega drain in Pokemon is a grass type move that works better leech seed or leech life
1000 pounds
Mewtwo can Mega Evolve into either Mega Mewtwo Y or Mega Mewtwo X.
Snorlax is a good candidate.