1) They do not translate the posts themselves. They translate just the phrases used in the vbulletin code. If you look at the Quick Reply box below - all the text shown there would be changed - Quick Reply, Message:, Options, Quote message in reply?, etc.
2) They should be able to, yes. I know they do sometimes on my forum. However, that may be a server thing you need to verify.
3) I've never done it, but I think it's just like installing a style or product - you import the xml file
4) You can ask in the
Requests For Paid Services