Can I upgrade my Windows 11 license from home to pro without reinstalling?

I have an ASUS tower PC about 2 years old.  I have been happily running Windows 10 Pro from a license I owned previously.  Now that Windows 10 is no longer supported, Microsoft has "upgraded" me to Windows 11 Pro, overwriting Win 10, but is unlicensed and so limits my Win 11 functionality.  For example- I can't change many of the Windows settings.  I am blind and need to change a number of settings just to use my computer.  My desktop is  constantly prompting me to provide a Win 11 Pro license key.

I tried using the Win 10 Pro license key but that didn't work.  I tried installing Win 10 and 11 dual boot, but my PC doesn't allow dual boot.  The ASUS PC includes a license of Windows 11 Home, but I can't use it with the installed Windows 11 Pro.  I could install Win 11 Home, but that would start from scratch and lose some of my local data and put my settings back to default, which in my case would be ausability nightmare. 

The easy way out is to just get a new license for Win 11 Pro.  Then Windows and the settings  would just stay the way they are, and enable all of my apps,data and settings.

1. To keep this from getting too expensive, can I buy an upgrade license from Win 11 Home to Pro?   If so, can I use it without reinstalling Windows 11?
2. If that doesn't work, can I downgrade my installation of Win 11 Pro to Win 11 Home without reinstalling?
3. If neither of the above is possible, I’ll have to just buy a new license of Windows 11 Pro.  Where do I get that?    Are there any options to keep the cost down to that of an upgrade rather than a net new license?