Certainly be worth trying the spare. I've heard something can go wrong with the ignition collar that reads the key, but not actually had chance to play and see what goes wrong.
Hope the spare works fine, its certainly the easiest solution if it works.
Various arguments about how long you have to leave the battery disconnected to reset the ECU, some say 24 hours, some say an hour, some say a half. Mines always reset on half an hour, error codes gone, windows going funny (they lose their automatic open and close, sometimes one side sometimes both). Car might go a bit lumpy because it has to re-learn all the timing mapping etc.
In a time of universal deceit - telling the truth is a revolutionary act. George Orwell
When the debate is lost, slander becomes the tool of the loser. Socrates