It depends on the state. In some, yes
but I'm sure others have provisions requiring some kind of disability if you want to take a test on more than 2 wheels.
yes, but you are limited to the size and power level of the bike you use for the test.
Yes! Please see all the requirements and procedures in the motorcycle manual (related link).
A trike is considered a motorcycle and requires a motorcycle endorsement on your driver's license.
No, you can get a 3 wheel vehicle endorsement. If you have a motorcycle endorsement, you can drive a trike but not the opposite.
No, you do not need a motorcycle to take the test.
You can take the motorycycle test even if you don't have motorcycle yet.
No.
you can take an official motorcycle drivers test at a residence that gives out the test or it could be possible that you could take an online official motorcycle drivers test.
Yes, you need to get it.
no
No, you do not need your own motorcycle to take the test. Many testing centers provide motorcycles for the test.
In the UK, yes.