a. Well, You should be able to cut off the hudraulic pressure from EDP somehow in case of overheat, or low pressure, or engine damage etc.
b. Most probably to disconnect the pump from engine driveshaft and therefore shut off the pump.
c. Every aircraft has some EDP or EDP fluid pressure shutoff mechanism. 738 has a solenoid for that (Which only cuts off pressure, creating a fluid circuit without stopping pump itself), A350 obviously has a clutch. Why not?