There is only one available for any and all WJs (Acess Point 2 for the last 10 years or more.).
Most likely not!
WJ4 is the third incarnation, I believe. No difference in monthly fee.
I can. PQ is just like a wired Joey. Mine is located about 20' from AP. You have to jump through an additional screen hoop to get to settings which is no big deal. As Scott said, it has Android which is nice, but I never use it. I BOUGHT it because I could not stand the lag the old, 2nd...