I do expect you use the English version. If so, unfortunately you cannot get either legally :(
- Genesect is absent from the Pokedex 3D Pro, unfortunatly.
- Meloetta can be gained via this method:
To unlock both of Meloetta's Formes, one must create a quiz in quiz slots 37-39, with the password of RGFOAUTF, and complete the quiz (Japanese Version only).
So in the English version, Meloetta is also absent.