1 :- what is the difference between initiator and catalyst???
Catalyst ??
Ans :-

 Catalyst  

is a substance that makes the reaction fast but recovered at the end of the reaction. It increases or decreases the rate of the reaction depending upon conditions(Pressure, Volume,Temperature, Chemicals)  provided.e.g Ni, Cd, Pd, ethylene, formaldehyde, sun light etc

Initiators  

is a substance that initiate the chemical reaction it can be a catalyst but can't be recovered at the end of reaction generally. An initiator act as catalyst when rate of reaction is desired but in general sense it is difficult to isolate the initiator at the end of the reaction.e.g Chlorine radical under sunlight