Can a parent stop me from leaving the state at 18?
They can't legally stop you from leaving. They are also under no legal obligation to continue providing for your needs.
If you are 18 your parents can't legally stop you. They can stop paying for your school, food, cell phone, internet, and who knows what else you get from them if you refuse to obey their rules. Your choice.
Absolutely not But by the same token, don't expect a place to live when you return
You can leave, but they do not have to let you back in.
Nope - but they can kick you out of the home.
Do they have to make it easy? NO Do they have to pay for it? NO Do they have to ever deal with you again? NO Do they have to let you back in after you leave? NO It sure is fun being an Adult. You can now do Adult things all by yourself. Many great things to experience out there. You also as a new Adult get to be responsible for your bad choices and pay any consequences.
real estate guy
If you are 18, the answer is no.
No they can't stop you as you are an adult. But you may not have a home to come back to if you do go. Is that a risk worth taking? Do you own the car that you are going to use to get there?