Windows 10 includes a Go back to the previous version of Windows 10 option in Start, Settings, Update & Security, Recovery. If you have issues after an in-place upgrade of Windows 10, you can use this option to downgrade to the previous Windows 10 version. For example, you can downgrade from Windows 10 version 1809 (October 2018 Update) to Windows 10 Version 1803 (April 2018 Update).
 

Some McAfee products do not currently support the use of this option to perform an in-place downgrade of Windows 10. Those products are listed in the Environment section of this article. These McAfee products use some common core components and drivers. A downgrade might cause these components and drivers to enter a corrupt state. A wide range of McAfee product issues could occur after you try a downgrade. These issues include critical services failing to start, which might leave the systems unprotected. In addition, it might require significant effort to get the McAfee products up and running again.