@YeJun4
It is not illegal for someone under 25yrs old to book an entire home. Whether the Host will permit someone to book at a certain age depends on their specific rules and if any local Homeowners' Associations require a specific age or not. Some Hosts do have a minimum age requirement and require photo ID either before or after the booking, or at check-in.
Sometimes Airbnb will flag a reservation as a "party risk" and prevent the reservation from being completed, or cancel the reservation as a party risk. The only way to know is to read the House Rules and message the Host about reserving the home. They likely will have some questions for you, especially if it is a large group. Most Hosts don't allow parties at their homes.