A 21 year old is legally an adult, while you can adopt an adult child you cannot be awarded "custody" of them unless they are mentally or physically disabled to the point where they cannot care for themselves.
no see links below
Yes, if the state require consent from the legal guardian since the non-custodial parent is not the legal guardian. And yes, because the non-custoduial parent does not have the legal right to make that kind of decision for the child. The non-custodial parent could face sanctions from the court. The custodial parent could sue to have the non-custodial parent pay to have the tattoo removed.
Generally, no. The parent with legal custody has the right to make the day to day decisions. Of course, the non-custodial parent could take the child to get their license with the permission of the parent with legal custody but not without it.
That depends on the policy.
you would have to take the matter to child services but i believe so.
If he has a court order I think he can.
Only with approval of the court. see my profile
If there is a court order to that affect the child and the custodial parent must adhere to the terms of the visitation order. If that does not take voluntarily take place the non custodial parent can petition the court to make visitation mandatory. The exception would be if by allowing a minor child to engage in visitation with the non custodial parent it would place the child in an environment of neglect and/or endangerment.
Not arbitrarily. The custodial parent would have to receive permission from the court for the change in residence.
Yes
Then the child should petition the court (or have the non-custodial parent petition the court, more likely) to modify the custody order. If the custodial parent is "gone for most of the year" and leaving the child in the care of someone else, the court will probably consider that a significant factor.
NO, a judge can take it into consideration, but at no age under 18 can do that.