no
Child support in Ohio usually continues until the child is 18, and up to the age of 21 if the child is in school. Whether or not you have to pay child support if the child is living with the noncustodial parent depends on the support order that it is in place Typically you can expect that you will have to expect to pay support.
Yes, depending on state laws. But, a motion to modify can be presented to the court. see links
How does the two interfere with each other?
Yes, there's no statute of limitations
Being 18 makes you an adult and with that privilege gives you the right to make your own adult decisions you can move in with who you want. And no one not even the custodial parent can keep you from making your own mind up. You are free to make your own decisions. As far as Child support in most states that is discontinued once the child reaches the age of 18 unless there are back child support due by the noncustodial parent. Once you reach a certain age custody is no longer an issue the child can make his or hers choice on which parent they chose to live with.
Age the age of majority, when they are also allowed to end visitation to school.
It's best to file a motion for change of custody, but you can start by contacting child support enforcement to present evidence that the child is living with you, though you may need to wait until after school starts.
File an emergency motion for change of custody see link
The school system will send out a truancy officer, who will site the child for truancy and the custodial parent for allowing it. Your friend, the noncustodial parent, has recourse in civil court. He/she can take the custodial parent back to court (with the school records) and file to be named managing conservator.
Contempt of Court, which is consider a Change of Circumstances as regards a custody change. see link below
Your question is unclear. Do you live in another state and what is your intent? see link for help
Yes, unless otherwise provided for by court orders. If you have an issue with the child attending a religious school then you should consult with an attorney and explore your options for transferring the child to a non-religious school especially since many religious schools do not follow a modern science curriculum.