A:Answer No, this is only a 900w UPS so it would not supply enough power to operate the gate. It could keep the controller alive, but if the gate was triggered to open, it would overload the UPS.
The 20 amp breaker would supply up to 2400w of power if it was fully utilized. The gate motor probably doesn’t draw that much, but if it requires a 20-amp breaker then it probably draws in excess of 1500w and, as I mentioned, this UPS is only designed to provide up to 900w.