The same level of any kind of Pokémon game lv.42
Rhyhorns evolve at level 42.
lv 42 as always, rhydon then evolves if traded with a protector
Stantler does not evolve.
graveler doesnt evolve at a level, you evolve it by trading.
Level 20.
Level 20
Level 23. 
it will evolve at lv. 20.
Your Aron will evolve at level 32 into Lairon.
14
35
Level 27.