Help please

18, otherwise the courts are involved in making the choice.

The child can choose at 18.

Beyond that the parent that does not have custody will have to make a motion in court and show to the court why you need to live with them.

It depends on what state you are in. For the state of Tx you have to be 12 years old to have a say so, but at 17 you are legally considered an adult and can even move out at that point. And I believe it's 16 years old when you can "divorce" your parents. I forget what the procedure is called. Just call your local sheriff's office and ask all the questions that you want answered. That's how I got out on my own

A child being offered a chance to tell the court whom they prefer is NOT the same as THEM being able to make the choice. The court is under no obligation to follow the child's wishes. This link referring to TX specifically.

Texas Child Custody Lawyer Explains Child?s Voice in Custody Hearing