Yes.
You catch it at mistral ton cave
You find Cobalion on Mistralton Cave.
I would use either an ultra ball or dusk ball.
It is a rare pokemon, but it is not a legendary pokemon
Unknown is not a legendary Pokemon but it is considered rare. Legendary Pokemon are one of a kinds.
no lileep is not a legendary pokemon but it is an ancient pokemon
Groudon, Kyogre, and Rayquaza. Groudon is the fire legendary pokemon, Kyogre is the water legendary pokemon, and Rayquaza is the air legendary pokemon.
Arcanine is not a legendary Pokemon because legendary Pokemon can't be breeded and arcanine can.
The legendary is palkia
No, snover is not a Legendary Pokemon
No, Blastoise is not a legendary pokemon.
Noivern is not a Legendary Pokemon.