No.
It can be found in MT Pyre.
mt pyre
search on mount pyre
lvl 37
Duskull will start to evolve into Dusclops once it hits Level 37.
sky pillar or evolve a duskull
you evolve a duskull at lvl 37 one of the best ghost Pokemon on emerald
I don't know but i think you can.
you evolve it from duskull or catch it in tower with the two orbs
It is very rare but you can catch it at mount Pyre.
Migrate from Ruby (or Sapphire/Emerald) or trade with Platinum
You can't catch a Haunter in Emerald. You can trade for one, you can find a Duskull/Dusclops at MT Pyre, but you can't straight out find a wild Haunter.