A plain key likely won't start the car I'm afraid.
Most Jimnys use an ignition immobiliser key, with a chip inside the plastic part. The security module has to be programmed to accept a new chip key.
This costs a very very very large sum of money, because it is so difficult to plug the diagnostic tool in and follow a few onscreen prompts
I imagine a similarly expensive procedure is required to match a key with the remote door locking plip.
However, if you have the misfortune to snap a key off, you can get a plain key cut at the local keybar, then attach the broken off key on the same ring, and the chip in the old key will be close enough to the receiver around the lock to work the ignition.