It's not an idiom. Idioms make no sense unless you know the meaning already. "No end" means just what it looks like -- something is endless.
for days and days (Portuguese - dias a fio )
One idiom that refers to a reward is "the pot at the end of the rainbow".
If you put something to rest, you solve the problem and end things.
it is when you are in a situation that is scary and frightening or dangerous, and the hair on your body stands on end.
Yes.
People mean that it is the end of the world/
It is not an idiom, it means your nose is itching.
It's not really an idiom. It means "what are you thinking about."
RFP is not an idiom. It's an abbreviation.
as wise as an owl
"Sieve" is not an idiom. See the related link.
It's not an idiom. It means the tip of your nostril.