I think there are three angle of attack sensors in all Airbus planes using fly-by-wire systems. The first two, which are arranged symmetrically near the nose are the main ones and the third one in the aft.
The angle of attack data is not typically displayed to the pilot. The computer, on the other hand displays only stall warning.
The angle of attack sensors are heated and active at all times. The data from the sensors is received by the computer, compared (voted on) and displayed in the cabin. The computer needs two values to agree for display.In case one fails or no two agree, the stall warning is lost.
The main use of the angle of attack sensors is their use by the computers in calculating the characteristic speeds and for providing stall warning. I don't think the pilots can monitor. let alone control the heating of the AoA sensors.