Protection of employees is weaker than anywhere else in the US. The Northern Mariana Islands have been accused by the US Federal Government and various other organizations for enslaving foreign workers (particularly from China and the Philippines) and immigrants in sweatshops and prostitution.
It can be as low as 18 or as high as 21 depending on where the child lives. In Delaware, the age of majority is 18. However, almost all states allow the child, a parent or a guardian ad litem to write to the judge and/or petition the court for modification of the original custody agreement.
There is no specific age nor can the child pick the parent. He or she can express a preference. However, remember that the policy of the law is for children to have two parents and for frequent and continuing contact with each. There are three ways a child can be heard in addition to speaking with his or her parents direcdtly.