Meaning: (with) all one’s belongings.

Example:
Tired of their tantrums, the landlady asked her tenants to vacate the house, bag and baggage, in a week’s times.

Meaning: take a less important position.

Example: The founder of the company decided to take a back seat and let the board members run the business.

Meaning: to take indirect or unofficial route to get something done. To be dishonest in order to do something which is either of meaning or value

Example Sentences:
1.- The agency was given to him because he slid into the contract through the back door.
1.- She thinks that as long as the purpose is true, using the back-door to achieve it is absolutely fine.

Meaning: celebrate; enjoy oneself.

Example: After the completion of the exams, the students decided to push the boat out and have a party.