how do I open a trunk on 92 lasabre, key won't work, glove box won't work

you can take the back seat out ...

It may be as simple as replacing the key since both locks will not work with this key. Do you have a spare you can try? If not, I would first replace the key by having a new one made. If you have the info, there is a key number assigned by GM for that VIN vehicle (it also came with the original keys and paperwork for the car). Use that number and get a new key from GM. A key cut at the hardware store will likely have the same problem as the one that you have.