Hello @~OSD~
The answer is Yes, and it is documented here in FAQs:
Can I use a Windows 10 product key to activate Windows 11?
Yes, users can activate Windows 11 using a Windows 10 product key. If your system already has an assigned digital license for Windows 10, it should automatically activate.
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Can we use the same product key of the windows 11 to downgrade and use it in the windows 10 to activate the new windows
Bcoz their are so many applications crushing so need to downgrade