They'd be called that person's relative.
When a person imitates another person, it is called mimicking or copying.
That is called a metonymy. It is a figure of speech where one term is substituted with another term that is closely related or associated with it.
A person who comes from another country is called an immigrant.
the person is called a chaufer
A person who says one thing and does another is called 'hypocritical'.
The person who speaks for another is called a spokesperson or a representative. They convey the thoughts, beliefs, or actions of the person or group they are representing.
If written by that person, it's called an autobiography. If written by another person, another author, it's called a biography.
A person from another country is typically called a foreigner or an international person.
Person under control of another is a puppet
Prejudice, discrimination, judging?
This person would be referred to as one who advocates discipline ( disciplinarian ).
A person who translates one language to another is called a translator.