Back pressure control valve

In what context? What is the working fluid, temperature and pressure?

The working fluid was sour gas at pressure 1500 psig and temp. 150 F although I think the usage of such valves(valve type) doesn't depend on the pressure and temp. but affect the valve size, trim material, etc

there is no difference between all three. Back pressure valve means the valves postion is set in order to automatically maintain a constant pressure on its inlet side. A pressure control valve recieces a signal to automatically hold a constant pressure on eith its inlet, outlet or some other pressure in the system. A choke valve is a control valve that typically has a manual set postion that allows a reduced flow through the system, it can also be set to automatically controll the flow through a syste,