When an older version of a page needs to be restored, select the page and click on the More tab, then select Versions (see image below).
Cascade displays (see the image below) the previous pages, their names, the date they were modified and who modified them. Select a previous version to view it.
For each of the previous states, the following options exist (see image below): View a Newer, Older or the Current version or Activate, Delete or Compare the file. After viewing several previous states, the correct file can be activated.