Windows 11 Pro (FQC-10545) Install

NitkaMittal 

Hello NitkaMittal!

Sure, we'll guide you as much as we can.

I am not an microsoft employee but after 5 years of Windows experience, i do know to install Windows 10 Pro, You DO NOT need to downgrade your product key or serial or anything. To install Windows 10 Pro just make sure your Windows 11 Product key is for Windows 11 Pro! So that after installing Windows 10, Your activation is gonna be right.

Please notice that the customer you have keeps the Windows 11 Disc installation unused and useless, Unless they needed it to upgrade again from 10 to 11. Only the product key on the box is needed, So let them know about this situation.

However, To install Windows 10 on MacBook after 3 years of experience , i do know that you just need to download Windows 10 ISO from Microsoft's Website which i'll put the link for you, and mount or write it to a USB... If the MacBook is almost after 2019 or late 2020... You don't even need a USB.

Newer MacBooks use the ISO itself. Please note: Your Windows 11 Product key might not work in Windows 10 Setup installation, It might work but there's a high chance it may not. In that case, Use a KMS Generic product key which is: 
VK7JG-NPHTM-C97JM-9MPGT-3V66T

W269N-WFGWX-YVC9B-4J6C9-T83GX

( These product key's does not activate your Windows 10, its only for just passing the Windows 10 Setup, You may just skip using the Skip button but just in case you needed a generic key )

Once Windows is installed, Use your Windows 11 Product key to activate your Windows 10 Pro. And thats everything you need, Its Done.

Feel free to reach back if needed. Here's the microsoft ISO Download link for Windows 10 Pro:
https://www.microsoft.com/software-download/windows10

Thanks

Ehsan G.