Yes it is legal.Is this moveset legal on an Arcanine?
-Substitute
-Thunder Fang
-Agility
-Flare Blitz
Thunder Fang is a tutor move i think once you evolve it to arcanine, so you lvl up till growlithe learns agility and crunch, evolve using fire stone, use a TM to give it sub, then tutor Thunder Fang onto it.