(1) What is the meaning of "The whole nine yards" ?
(2) When do we start greeting "Good Evening" and when "good night"
Here is another thread with a question about "the whole nine yards":
The expression means "everything" / "the whole thing". (No one knows the origin of this expression for sure, but I'd say there is no connection to American football!)
Good evening is a formal greeting. There is no "official" timeframe for its use, but I'd say it would be used after 6 or 7 p.m. I doubt that I'd use this expression in an informal situation (I'd say "Hi" or something similar instead.)
Good night is used in the sense of "goodbye" (i.e., a departure), usually in the late evening or at night, or when someone is about to go to bed/sleep.