I only know one cheat in the pokémon series and that is the "change box, turn off while saving and copy a pokémon" cheat from Pokémon gold, silver and crystal. After that they changed how the computer works, so that cheat isn't possible to preform anymore.
Then there is AR, but I only count AR as cheating if you use it to teach an attack to your pokémon that it normally isn't able to learn at all, or when you make it extra strong with some stats cheat.