Varies from state to state, as a rule of thumb if you can't register the vehicle you will probably have similar problems in other states.
Over powered,
Major suspension modifications,
Open wheeled,
"Straight Pipes" exhaust,
are examples of things that will present problems registering the vehicle.
NO
Not in Oregon or Washington, but how you use it can be illegal.
In states where cars have to be inspected it is illegal. In the UK it is illegal.
liened vehicles
It is illegal. Don't do it
Yes.
Nope.
Buggati
Yes it is illegal. It is stealing and you can be arrested.
Yes, that's illegal.
no its illegal
Yes