First off, I want to make it clear that, at this stage anyway, nobody will be forced to upgrade to Windows 11, it will be offered as an optional upgrade. Whether or not that will change in the future, particularly nearing Windows 10’s end-of-support date, remains to be seen.
Try Out Windows 11 For 10 Days
Apparently, the “try for 10 days” option was explained in a PDF document issued to manufacturers:
Can I go back to Windows 10 after I upgrade if I don’t like Windows 11?
Yes. After you have installed the Windows 11 upgrade there is a 10 day period where you can move back to Windows 10 while keeping files and data that you brought along with you. After the 10 days you will need to back up your data and do a “clean install” to move back to Windows 10 ~ source
If your computer supports Windows 11, and you want to take it for a test run, you can do so for up to 10 days before making a final decision. If it turns out that you don’t like Windows 11 and would prefer to go back to Windows 10, rolling back is quite simple; just go to Settings > Update & Security > Recovery and choose “Go back to the previous version of Windows”. If you do that within 10 days of installing Windows 11, you can go back to Windows 10 without losing your files and installed programs.
If you somehow inadvertently install Windows 11, the same deal applies — you will have up to 10 days to go back to Windows 10 without losing anything. So, if you do inadvertently start the upgrade process, do not panic and try to stop the upgrade. If you turn off the PC or interrupt the upgrade process in some way it can potentially cause issues that might not be easily rectified. Allow the upgrade to complete and then use the rollback option to go back to Windows 10.