No, step parents do not have any legal rights to the kids.
He can be Guardian if parents allow.
None.
no
ALL rights. You're still a child.
No
Yes.
Yes, it is.
The same rights they had when they were younger. Your child is not 18 yet.
Parents are responsible financially for a 17 year old in Michigan who voluntarily moves out of the house unless the teen is completely emancipated. Teens can be partially emancipated, which means parents can still be responsible for certain things.
The legal rights of a fifteen year old towards his or her parents differ from state to state, country to country. In some places they have the right to "divorce" (as it is called in the United States) their parents. In other places they do not have many rights until they reach an older age.
Most likely they can call the cops and make her move back, so I would suggest to you if she moves out and is living with you, to make sure the parents don't even have a clue where to search for her.
Yes, the parents would still be responsible for her until she reaches the age 18.