Pokemon Legality Dealing with VGC

[Chasey452]

Alright I am going to enter VGC, but I think I may have messed up. Anyways here is a few questions:

1. How do they check if your Pokemon or Items are hacked in VGC?

2. I used a AR Code to make all pokemon caught Modest. Will I be in trouble and removed from the VGC with the technology they have to check legit pokemon.

3. If I have two hacked parents and a legit offspring, will they detect anythink wrong with the Pokemon?

Thanks!