On the house means it's free, or that the person who says that will pay for whatever you got.
This is not an idiom. When you compare two things by saying one is the other, it is a metaphor. It means that however you keep your house reflects your personality, and vice versa.
It means you do not have to pay for dinner,either it is free or someone else will pay for you. This idiom usually means the 'house' or restaurant owner will pay for not 'anyone'.
In trouble. The image is of your spouse kicking you out of the house and you have to spend the night with the dog.
yes
It's not really an idiom. It means "what are you thinking about."
RFP is not an idiom. It's an abbreviation.
It is not an idiom, it means your nose is itching.
idiom means expression like a page in a book
It's not an idiom. It means the tip of your nostril.
"Sieve" is not an idiom. See the related link.
It means to compromise and negotiate. Imagine traveling halfway to someone's house to meet them instead of making them come all the way to your house.
This is not an idiom. It is a measurement. $100,000 is how you write it in numbers.