I'd sure like to know how you two are upgrading from Win7 to Win11 for free. Lets see some docs. I'd like to know how it's done. I couldn't no matter which route I took. I couldn't even go the paid upgrade route. The process would ALWAYS fail and revert. But how is that possible? Windows upgrade NEVER has any errors. So it worked for you, without a How-To what's that mean to me?
If you went 7 to 10 to 11 that hardly counts. That path WAS free.
Lorings.
NewMelle
Activating Windows 11 with a Windows 7 key only works if you opted in to the Windows 10 upgrade first. If you didn't your SOL with that key. You can also skip the product key issues if you link your OS with a MS account. It'll just activate next time you sign in with that account.
Microsoft finally fixed the "Bug" that would let a windows 7 key activate Windows 10 past the deadline if you didn't opt-in first, like 3 years ago.
For upgrading from 10 to 11 any issue I've had actually upgrading to a new major build of Windows, has been something stupid I did, some 3rd party app, drivers for really old hardware. Things I tend to stay away from, Classic Shell, CCleaner. McAfee, Norton, "Professional uninstallers". Also having hardware that meet's the minimum helps too. 
I don't think it's possible to go straight to 11 from 7, without first stepping through 10. I've also never tried.