Greetings, and welcome to PlaneShift! :)
1. PS has been in 3D development for about 5 years now. It is a pre-alpha, version 0.3.012.
2. The server experiences crashes every now and then, but usually resumes on the same day, and the crashes are not frequent enough to make playing unbearable.
3. The best site with a lot of information is the main site, though the forums work too.
4. There is only one server currently, Laanx (hosted by Fragnetics), but more will be added when the world expands enough to need it. All servers will connect to the same world, so all players will play with each other - there will be no separation.