1. Yes, some Voyager aircraft will have a centreline hose, but not all. I believe it is five centreline but don't quote me on that.
2. I believe it is an A340 wing married to an A330 fuselage to make use of the outboard engine hard points on the A340 for the wing AAR pods.
3. Unsure how common this is, but wouldn't think it is that common as why would you use a different wing for civvy jets?
Hope this helps.