No. The passport is all you need.
No. You need to begin the process of naturalization to become a Mexican citizen.
She should not even need a visa, as your wife, if you are a citizen of England.
The related link below will provide you with the answer to this question.
Of course; all you need is a valid passport. No visas are required unless you connect flights in the United States.
Yes
A passport and a visa.
Of course not, because Cozumel is part of the Mexican Land.
Nothing, just your passport. Some other forms will be issued on the plane.
Yes, you do.
Yes
no
Yes the man from China will need a visa to visit the U.K.