RE: rear seat belts are stuck/jammed... how to unlock?
Have you installed them yet?
If you have them on the bench, laying down, they will be locked untill you put them upright in the installed position. There is a locking mechanism in there that works on intertia. When you slam on the brakes, the seatbelts lock. Now if your holding the seat belt sideways or upside down, the locking mechanism will keep the belt locked until the tension is relieved and the belt is in the upright position
If you have a question, ask it in the forums. I will no longer be answering questions sent to my email.