Hi @Inder Pal Singh ,
You'll find the official information about downgrade rights in the following Microsoft documentation:
Downgrade rights for Microsoft Commercial Licensing, OEM, and full-package product licenses
https://download.microsoft.com/download/3/D/4/3D42BDC2-6725-4B29-B75A-A5B04179958B/Licensing_brief_PLT_Downgrade_Rights.pdf
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Best regards,
Leon