SR = closing and opening the game until you get the Pokemon you want.
Power Save is an external device (hack) that creates a separate save file.
Clone = exact copy of a Pokemon, there are several ways of doing that this Gen.
(I'm not at expert on the methods)
RNG = figuring out how and where to start a game to get the Pokemon you want (basically figuring out exactly where in the RNG program the game is and if necessary re-starting it. Fairly common practice gen 5 impossible so far in gen 6 and more difficult and less common in gen 3 and 4)