I got two conditional offers. If I firm one and insurance another one, am I obligaed to accept my insurance option if I don't get my firm option. Here is the explaination from UCAS:
Insurance acceptance
If your firm choice is a conditional offer, you can accept another offer as an insurance choice. Your insurance choice can be conditional or unconditional and acts as a back-up, so if you don't meet the conditions for your firm choice but meet the conditions for your insurance, you will be committed to the insurance choice. You can only have one insurance choice.
The conditions for your insurance choice can be higher than your firm choice, but be aware that if you're not accepted by your firm choice, it's unlikely that you will be accepted for an insurance choice that requests higher grades.
You don't have to accept an insurance choice - if you're not sure about any of your other choices once you have accepted a firm choice, you're not obliged to accept one as an insurance option.