I thought that the spare key is just another piece of ordinally metal key, there is no transponder or micro chip in it ? To use it, it should works just like normal car keys, insert into the door key hole can open the door, and insert into the ignition lock can open the door.
For the i-key, the SE told me if the transponder is not working, or battery weak, we can withdraw the i-key and start the engine. Otherwise we need to bring our spare key everytime we drive, if not no battery cannot drive, then very mah fan liao.
Maybe you did not tell the locksmith that you want to duplicate the normal car key ?