salamance didn`t learn earthquake but you can teach it using TM
Milotic, Pikachu (with Light Ball), Salamence, Altaria, Kingdra, the three Regis (They aren't legendaries) etc...
Salamence can only learn Hydro Pump as an egg move in Pokemon Emerald.
There's quite a few: Altaria, Bagon, Shellgon, Salamence, Vibrava, Flygon, Kingdra (but you need to trade Seadra with dragon scale), Latios/Latias, Rayquaza.
Here is the list of Pokemon who can learn Fly: Salamence Rayquaza Crobat Zatu Skarmory Taillow Swellow Wingull Pelliper Vibrava Flygon Swablu Altaria I made Swellow and Flygon Learn IT.
I believe you can get it in the Sky Pillar
swampert altaria breloom camarupt raquiza flygon this is my team and I've beat the game no that's rubbish try swampert/absol/breloom/camerupt/salamence/armaldo
salamence is the last form of bagon salamence doesn't evolve again.
Get it at meteor falls in the way back
It evolves at level 55
Migrate it from LeafGreen, FireRed, Ruby, Sapphire, or Emerald
metagross salamence flygon blaziken swampert sceptile
Train a bagon to level 36 then to level 50 to get salamence.