See “Choose between the 64-bit or 32-bit version of Office” (link to Microsoft site).
EES - Windows OS
What is the “upgrade version”?
This means that the OS can be upgraded (changed to a higher version) only if it is already running a Windows OS.
If your PC already has a Windows OS when you buy it, you are eligible.
In the case of a Mac, the upgrade can be applied as an OS that runs on virtual environment software or boot camp that can run on a Mac.
Downgrading the OS is also possible, but not recommended.
What is the difference between “new install” and ” upgrade install”?
A “new install” installs a new Windows OS.
In contrast, an “upgrade install” inherits the settings of the original Windows OS.
Can I install the “upgrade version” to my self-built computer or computers without any OS?
You cannot install unless you have a license that you can upgrade from.
What should I do if I do not have any OS to upgrade from?
You need to separately obtain an OS to upgrade from. The upgrade version can be used if you have a package license that allows installation of a new OS.
Can I newly install a Windows OS by upgrading from an OEM product from a different computer?
No, you cannot.
Are there any restrictions on the versions or editions of Windows OS that can be “upgraded”?
Yes. Please check this table.
Reference: Windows 10 upgrade paths (link to Microsoft site)