Does anyone know how to remove back seat of 1985 4-door Oldsmobile Cutlass Supreme

remove the bottom of the rear seats first. Then remove the top of the rear seats. Now you can easily crawl-through into the trunk area to get your keys. Next chance you get, you might want to install an electronic trunk release mechanism in place of the mechanical one, connect it into the trunk lid light power harness and run a remote switch into the rear passenger area for future use and use some kind of push button in a hidden area. if you have a rear middle brake light in the rear window, you can even install a slim rocket or push button switch in that housing to hide it, yet remain available in case you ever need it. The electronic trunk release can be pulled from many old GM vehicles at an auto scrapyard, parts recycler, or even new from many online sources for little money.

Once you've done all that you will notice a metal wall that divides the trunk from the passenger compartment. It is there to prevent things from the trunk from coming through the back seat and entering the passenger compartment in the event of an accident. It is part of the structure of the car and is not removable. You will also notice that you are no closer to retrieving your keys than you were before going to all that trouble. Your next step at this point is to either call a locksmith to get you into the trunk, or get an auto body slide hammer with a large sheet metal screw in the end of it. Screw it into the lock where you would put the key and pull the entire lock assembly out of the trunk lid. Yes, the lock assembly will be ruined and need replacing. If all goes well, there will probably be no damage to the trunk lid itself.