A new iPad will work with 4G LTE in the US. You will want to get a micro-SIM for a US-based data plan to keep the costs down.
An iPad that you buy in the US will be just as functional as one you buy in the UK. Remember that you have to get a power plug that works in the UK.
all previous apps do work on the iPad but some are beginning to be designed especially for them. You can purchase them straight from the iPad or from the iTunes Store.
No
no
nope it wont
no because UK runs on a diffrent voltage system
yes >>wifi<< iPad means built in wifi, so you can get wifi on another planet.
Yes
Yes it will.
It will work if you can get a UK power adaptor for it, and if you have a NTSC compatible TV, but you will only will be able to play games from the US, not ones from the UK.
it is out
Yes, as the only connectivity it requires is Wifi (Wifi only version).