According to Serebii, Mega Mewtwo X is exclusive to Pokémon X while Mega Mewtwo Y is exclusive to Pokémon Y.
Which means that you're not wrong at all, Kushagra.

...

Also, those Starter Pokémon's evolutions D:
Chespin's evo looks more like a Pignite now! D:
Fennekin's evo... uh, yeah. It looks strange to me.
Froakie's evo looks awesome, in my opinion.

Also, those three Pokémon retain their types.
(Chespin's evo is pure Grass, Fennekin's evo is pure Fire, and Froakie's evo is pure Water.)