So let's say I have a Pokémon that was bred legally and is completely legitimate. Say I used a hacking device, and changed one of these:
None of these affect performance in wi-fi battles, so would I be able to use it if I wanted to enter a tournament? Shininess and ribbons I would guess not because they have an effect (sparkle if shiny, contest ribbon animation if you have the contest ribbon), but would the others still make this Pokémon banned?
In fact, even if you were to actually go and change a Pokemon's IVs, EVs, Abilities or even levels, they would be allowed. There are exceptions though. If you hack a Pokemon to make it illegitimate i.e,
... then your Pokemon will not be allowed in Wifi battles. The checking in VGC, however, is a little stricter.
Hope I helped!