Those pump oil anytime the engine is running, the pump is powered by the crankshaft not the clutch, if I remember rite the pump drive can be misassembeled, pull the clutch and give it some study. (I had 5 of them)
Nope, nope, nope, they are different. You can get by with l p on a standard 3/8 sprocket, it won't be right but will work. but you cannot put regular 3/8 on a lo pro sprocket.