I agree with Ken here. Make sure you are doing regular backups of Tableau server.
From a workbook standpoint, Tableau server will save previous versions of your workbooks (assuming that you are overwriting the workbook with each publish). Yo can see this by clicking the three dots next to the workbook name on the portal and select "Revision History":
Then you can download (using the three dots next to the Revision) or restore the desired revision:
The number of versions that are saved will depend on your server settings.
As far as a version control tool, you can use things like SharePoint or Confluence that allow versioning. The benefit of those is that you can also lock the workbook to prevent multiple developers from overwriting each others changes.
Git is also an option if you use .twbx files (simply .xml files). Merging changes doesn't work all that well but you can use the versioning/locking features.
Hope this helps,