@Felxnord Contributions are very welcomed !
I suggest you to check CONTRIBUTING.md and Technical README which includes how to add new language.
If you have any question it's best to use GitHub discussion since it's technical.
@PedroKeitawa You can. One of main PKVault feature is to passing a pkm from any Gen to any other Gen (if species is compatible with target save).
PKVault uses a logic of "variants". When you move a Pikachu from Gen2 to Gen3, a new "variant" of Pikachu is created for this generation (and attached to your pikachu, keeping them synchronized).
This logic of variants is required to avoid any data loss, like when you're doing Gen3 -> Gen2 (losing nature, ability, etc).
You can see more in the app: Help -> Storage -> Attached pokémons. Or here.