No, accessing the documents and using the online tools are all free of charge.
Yes, Cabinet Papers is a part of The National Archives' website.
This site provides comprehensive access to cabinet papers from 1915 to the late 20th century under restrictions imposed by the 20-year rule.
The records of the Cabinet Office are a major contemporary source material for British political history from the early 20th century. These records illustrate how British governments dealt with the major events of the 20th century.
How should Documents on this site be referenced?
See our guide on How to Cite Documents in The National Archives.