Can part of Integrated Circuit be damaged from heat gun usage?
carefully using heat gun

LOL!  Do you carefully use a lawn mower to trim your fingernails too?

Hot air can be used for soldering, but has to be properly controlled and applied.  Without a hot air soldering station with the right tip and the right temperature and airflow settings, you're just slicing deli meant with a chain saw.

Consider anything you removed from the board with the chain saw heat gun to be junk.  Toss it and move on.  Don't waste any more time and frustration with abused parts.