If I’m offered a place through Extra, do I have to accept it as my firm choice, or can I accept it as an insurance choice and send my application to another university or college?

You can only have one Extra choice at any given time, so if you receive an offer through Extra you must either accept it as your firm choice or decline it. If you decline the offer you’ll be able to add another Extra choice providing there’s still time. If you use Extra, you will never have an insurance choice.