So the final result of my R&D is, the prerequisite of the subscription upgrade license is that you need to have Windows 10/11 pro-activated machine (Activated by the digital key or by the retail key) because the subscription only provides an upgrade from Windows 10/11 pro to windows 10/11 enterprise and it does not provide windows client activation. This will automatically upgrade the Windows license, as long as the subscription is valid and the device meets the requirements. For this, you will need to have a Microsoft 365 subscription that includes the Windows 10/11 Enterprise E3 or E5 plan. These are the only plans that allow you to activate the Windows 10/11 Enterprise version on your devices using your Microsoft account. You also need to have a device that meets the minimum hardware requirements for Windows 10/11 and has a valid digital license or product key.