If so what level can you.

Yes, a shaman can.
As Enhancement they can use two 1-handed weapons such as fist weapons, one-handed axes, and one handed maces.
Whereas if your a resto/ele shaman, you can't. You can only use one-handed maces/daggers with shields. Or a staff.
I believe you learn to dual wield as enhancement at level 40

Yes if you are an enhancement shaman. I believe you get it when you reach level 10 and choose your talent tree.

Yes, however you must be specced enhancement in the tallent tree.

Pre bc shamans used 2 handed weapons with the shaman only enchant windfury to some times proc an extra hit, ie HWL Shamans or Hand of Ragnaros (if thats how u spell it lul) wielding shamans could do major damage, however modern day WoW (Cata) enhance has progressed past a slow moving proc class to a fast moving combat spec that alows the shaman to summon ghost wolves to your aid, and yes, you can dual wield.