Think about something being literally in a bag and you can figure this out. It means that something is guaranteed, foolproof, or sure to happen.
The idiom "not your bag" indicates that you're not good at something or you just don't enjoy it. Example sentences: The painting is ugly because art is not your bag. I didn't make the team, but tennis just isn't my bag.
It's a done deal - there is no chance of failure.
There is no such term as "bag pull" in the English language. Unless you mean "pull something out of a bag" which is an idiom that means to do something in the spur of the moment that solves a problem.
Nothing. However, a brown bag LUNCH means one that you pack yourself, usually carried in a paper sack.
The idiom is "dead certainty". It means it's in the bag = this is a dead certainty = this is cinch
This expression is an old style idiom for "he's all that and a bag of chips". It denoted an aggressively confident person who did not accept negativity.
It's not really an idiom. It means "what are you thinking about."
It is not an idiom, it means your nose is itching.
RFP is not an idiom. It's an abbreviation.
"Sieve" is not an idiom. See the related link.
It's not an idiom. It means the tip of your nostril.
idiom means expression like a page in a book