About monogamy, if I immigrate to a polygamous country, marry n wives, and then the whole family immigrates back, is there a problem?

First of all, China is not an immigrant country. If you emigrate, you can't immigrate back.

Third, when you immigrate to your wife, you have to prove that these people are your wives. In China, the government won't give you proof. Even if you turn yourself in, you won't be sentenced at most. )