Räven, take a Fletchling, Bulbasaur, and Bergmite.
It must not have its HA, nor should you teach it Roost.
It can only evolve into Fletchinder after solo'ing Grant. And again into Talonflame if it defeats that one Sky Trainer's Emolga just outside Reflecting Cave (without backup flyers), otherwise you'll have to wait a day to challenge her again until it's okay.
Name it Tweedums.
For Bulbasaur, it should not Mega Evolve, nor have a Tox-Seed moveset.
It can evolve into Ivysaur after defeating Corrina's Mega Lucario. And once again into Venusaur after solo'ing Ramos. (Hope that's not too bad.)
Name it RiffRafflesia (or RiffRaff if it doesn't fit).
For Bergmite, its ability must be Own Tempo, and cannot learn Ice Beam, but Blizzard.
It can only evolve into Avalugg and solo'ing two gyms of your choice (but none where it has an advantage).
Name it Titanic.