Changing World Servers

Yes, if you start a world you start from the beginning at level 1 (except on Vet servers where everyone starts at 45).

If you have time and resources you may play on as many worlds as you like. Many players start on a world well established to learn how to play well and then start on a new world when it is introduced.

Unless you have already joined the world, you can't. The older series of worlds are now closed to new entrants. Even with a link you can't join unless you have been there within the last 2 years (approximately).

Even some of the newer Tib/Firestorm/Wrath worlds are closed to new entrants.