I have been asked to flash a Samsung Tab Active 2 but although I've done several phones before I've got a question about general flashing..

What, if anything, will this do to the ability to 'find' or trace the device after flashing?
Actually, now i come to think of it, if the entire firmware is replaced does this render the device/phone completely cleaned?

It's a legitimate issue if you don't know the origin of the device.
Second hand devices often have no provenance/proof of ownership.
If i buy a galaxy 'x' from ebay and flash it and then resell it, i don't know the history of it.

Many thanks people