A few things about hacking.
The game does check for pokémon with illegal movesets and abilities. These cannot be traded on GTS. I know someone who tried to trade a hacked palkia with splash in all 4 of its move slots on GTS, the game said it cannot be offered for that trade. The same thing happened when I tried to trade a staryu hacked to have natural cure instead of illuminate. I assume the same checks are made for wifi battle tower submissions.
As far as stats, either directly hacked or hacked to have >510 EVs, I don't know. I do know that when you put a pokémon into the PC and take it back out it recalculates the stats from the EVs/IVs/Natures/Level so directly hacked stats don't stay through that. Stats are also recalculated when a pokémon levels up. My guess is that these hacked pokémon will work in the battle tower but won't get uploaded for other players to fight against.
I don't think the game could check for hacked 31 IVs, or shininess, or nature though.
The game does check for pokémon with illegal movesets and abilities. These cannot be traded on GTS. I know someone who tried to trade a hacked palkia with splash in all 4 of its move slots on GTS, the game said it cannot be offered for that trade. The same thing happened when I tried to trade a staryu hacked to have natural cure instead of illuminate. I assume the same checks are made for wifi battle tower submissions.
As far as stats, either directly hacked or hacked to have >510 EVs, I don't know. I do know that when you put a pokémon into the PC and take it back out it recalculates the stats from the EVs/IVs/Natures/Level so directly hacked stats don't stay through that. Stats are also recalculated when a pokémon levels up. My guess is that these hacked pokémon will work in the battle tower but won't get uploaded for other players to fight against.
I don't think the game could check for hacked 31 IVs, or shininess, or nature though.