In layman terms, the Content version is a simple process that creates a copy of the page content every time you hit the Save button. Requirement is Content Versioning in Joomla is activated.

How to Enable Joomla Content Versioning?

To enable Content Versioning in Joomla 4 is damn easy. Follow the steps.

• Navigate to Content > Articles > Click on Options buttons.
• Under the Edit Layout Tab, Find Enable Versions options. Select Yes.
• Once you enable the Content Version if you ask you to set the Maximum Versions, you can set any number of versions.

At last, click the Save and Close button.

How to Enable Content Versioning in ui/Theme-Builder Pro?

Content versioning was added with the last update v.0.0.55.

• Navigate to Components > ui/Theme-Builder Pro > Pages > Click on Options toolbar button.
• Under the Edit Advance Tab, Find Enable Versions options. Select Yes.
• Once you enable the Content Version if you ask you to set the Maximum Versions, you can set any number of versions. (This option overrides joomla's content article option)

Now you can navigate to a ui/Theme-Builder Pro page of your choice and edit that page. After you have saved your page click on the icon in the top left menu bar, you will find all the version of the page.
You can Restore, Preview, Compare, Keep On/Off and Delete version of the page.

How to Use Content Versioning?

Click on the Page settings icon in the top right menu bar.

When you will create a new page or modify the existing one, you will see a new tab on the Page settings modal with new fields. It will be Version and Version Note. You can specify a note for the edits or enter version like v1.0 or similar like this.
The Version field is automatically incremented when you save the page.