When Windows 10 first came out, you could only get the free activation if you upgraded an activated copy of Windows 7. On a couple of PCs & a VM I wanted to run both versions of Windows, so I performed a complete image backup of Win7, upgraded that copy of Win7 to Win10, then restored that Win7 backup to another partition. I added Win7 to Win10's boot menu with EasyBCD, & had to change one of the partition's Windows-assigned IDs [Admin. Tools -> Computer Management]. All of my software carried over from Win7 to Win10, and to date I haven't had any problems with those copies of Win10.
While some installed software might lose activation, the vast majority did not. If anyone wants to preserve their GOTD apps, and also wants separate copies of Win10 & 11, perhaps that above method might be the best way to go about it.