CPU will be fine, this has happened to me before, cheap thermal paste turned almost to glue on a old socket 939 system and when I pulled the heatsink off it lifted the cpu with it even tho I did the normal slight turn left and right before lifting.

Edit, aslong as you didnt heat it too much with the heatgun.

Yeah, this seems to be common with 478 and the like. Never had one not work when put back, though I suppose it is possible the IHS could separate from the die I don't think it is at all likely and I'm 99.99% certain it will work without any complaint whatsoever.

Yeah, this is pretty frequent with this socket. I had it even come out with one pin slightly bent once, but it was possible to carefully straighten it.

The thermal paste dries up and holds strong. In the absence of a heat gun or other materials to dissolve it, one method which generally works is to hold the CPU in one hand, the heatsink in the other, and twisting them against each other in opposite directions. Essentially, this is the same "slight turn left and right" thing that FaSMaN mentioned, except done after the extraction.

Putting them in the oven at 60°C works too.

The heatsink could also be put in hot water for a while with the CPU upwards. There are many ways to soften the thermal paste.

One question about 478 socket bracket. Is this bracket normally shipped with 478 socket motherboards or should I also remove it if getting some other motherboard later where to put the CPU?

It normally comes attached to the board.

Indeed, but it can't hurt to remove it if you aren't going to use the donor board for anything else. I kept the plastic crap from a 939 board once and though it took almost a decade, I ended up with an AM2 board from which it had been removed. My forward thinking sure saved the day, especially when I remembered how unreliable the AM2 platform was (at the budget end of its market) and promptly sold the board to someone else.

AMx retention brackets normally arent a problem as all of the good replacement HSF normally come with a bolt trough replacement so a person tends to have a few spare .

the other way to do this is start computer, unplug the heatsink fan for 30 seconds, kill power to system and pull off heatsink 😁