when i tried to replace my cpu fan there is this back plate
Trying to install a hyper evo 212 cooler
you are not just replacing the CPU fan, you are replacing the entire heatsink.
and when i mention gently
prying off the backplate with a flathead screwdriver;
this is after you have removed the entire heatsink and all standoffs, bolts, screws, thumbscrews, etc
and all that is still remaining attached is the plastic backplate.
this would not damage anything on the board because all you would be doing is lifting off the backplate that is no longer fastened in place.
any double sided adhesive would easily be torn through with the flathead, much easier than trying to pull dental floss through it.