Any hospital will treat you regardless of whether you have insurance. Your insurance company can't charge you more for getting emergency room services at an out-of-network hospital.
Insurance plans can't make you pay more in co-payments or co-insurance if you get emergency care from an out-of-network hospital. They also can't require you to get prior approval before getting emergency room services from a provider or hospital outside your plan's network.
This depends on the plan that you chose and the hospital you go to. This care may be subject to a deductible, for example, or a hospital may have particular rules in place.