How does it appear and is the code permanent, like it doesn't disappear again?
The code appears with heat friction and yeah it's permanent. It will appear again when you rub it again. It's gonna go back to normal after awhile so there's no use, until the onine thing is released.
The DNA code is the black thing. It took me awhile to get it, try breathing on it while rubbing it. That's what I did. Get your fingers all warmed up first.