What is illegal and what is legal with figure fours and scissors? ( around the legs, head, and body ) And what is the difference between figure fours and scissors?

I have long legs so I am tempted to use these moves.
And is this move illegal or legal?
YouTube - Deadly Weapons II Chickenwing

I want to practice that, but it looks like a choke to me; especially if you squeeze your legs hard. Is it worth learning?

Thanks