Hello @Hayley-Nathan-Shelley-An0,
Others may be able to offer suggestions re the book 6 nights get 1 free question.
It is possible to set a minimum number of nights stay for a specific period.
Go to your calendar and clikc on "Manage settings" in the top right hand corner.
Then click on "Availability" and then on the "Edit" button for the "Trip length" section.
Scroll down and click on "Add a requirement for seasons or weekends" and click on the "During" box.
Select "Specific dates". Now enter the start and end dates and the minimum number of nights.
Then click "Save" twice.
Steve.