Before at all, do buy the check 1st,  to know about ur mac situation, for best support:
 
https://www.biosunlocker.com/product-page/check-for-activation-lock-on-mac-imac
 
U got any of pictures above ?
u did check and u found FMI ON ( iCloud Activated )? ...
just do pay and contact me, it can be unlocked permanently ...
Unlock process delay depends between INSTANT to 5 days .
 
what u need :
 
1. 2nd working Mac updated to late Big Sur
2. Type C cable
3. Install "anydesk" on the working Mac
4. Good internet