Does the v6 model have AWD like my v8??

[M1911]

So, on my 2007 Ltd V8 4wd, I take from this thread that I am in AWD always, and that I can lock the center diff with the button.

Yes, it is always in 4WD. Only lock the center diff on loose surfaces (or if you lock it on pavement, don't make any turns).

Is the turning knob on the right side of the steering wheel just a choice between Hi & Lo?

If you look at the knob, it has two positions labeled H4 and L4. That should be a clue.

My 2000 had a locking rear diff option, but I don't seem to have that on this newer version.

Only the 2009 Trail Edition had a locking rear diff, but finding one of those is like finding a unicorn.