1 + 2 off so you can use the switching panel to display air data information on either side, allowing both pilots to have the controls. It helps during app preparation and briefing, and also allows some sort of fatigue management as neither AP nor A/THR would be available for the reminder of the flight.
Gear extension and retraction is available whenever ADR1 or ADR3 are available, show your FO the logic diagram in the FCOM.