You hire a non-citizen the same way you hire a citizen - offer them a job.
Your new employee will need to provide proof of eligibility to work in the US, however. Generally speaking, this will be a valid US Visa that specifically states the owner may hold a job, a U.S. Permanent Resident visa (which implicitly allows for job-holding), or evidence of US citizenship. See the CIS form I-9 for a complete list of acceptable means of proving eligibility to work.
If the non-US citizen has a valid visa for employment, they are treated exactly like any citizen employee.
If you wish to hire a non-citzen who does NOT currently have a valid work visa, you (the employer) may try to sponsor them for such a visa. This can be very difficult and expensive, and one should talk to an Immigration lawyer about the process for obtaining a valid work visa for a foreign alien worker.
No, just the child.
A non-citzen can become a citizen in the US if they follow the proper procedures.
yes
Vote.
A citizen can petition their parents if the citizen is at least 21.
obviously not
Not legally.
Marriage is a wonderful event. Yes, if a female US citizen legally marries a non US citizen in the state of Michigan, they are indeed legally married.
look in a social studies book 4 cryin out loud
You go to immigration and start the paper work.
yes.
that's a maybe