Any part more complicated than a screw or rivet likely has a serial number / part number on it, and if it does, could be traced back to the exact aircraft it was installed on.
And even if there are no serial numbers, there are detailed maintenance records for the aircraft; you can see if a bolt has been replaced, trimmer adjusted or a hole fixed, and you'll find matching records in the books.
This used to be kept in paper log books. Now these records are computerized.
Yes of course, "in the books" was just an idiom here (perhaps not the exactly correct one). What has been done to the plane is a matter of record and can be checked.
Of course. I wasn't disagreeing with you.
Yes. On the aircraft I work on, serial numbers often contain a few digits that are aircraft specific.