If the battery is disconnected are the programmed codes (seat position, auto door lock etc.) lost ?
If so, should another battery be connected to the posts under the hood before and during the time the battery is disconnected?
I don't think so. Aren't some of those key codes? I bet it's like flashing a BIOS in your computer. It would be pretty clunky if every time you disconnected the battery you had to reprogram the car.