I have used snap-on diagnostics for the last 15 years and have a solus pro and other snap-on machines they are so easy to use and idiot proof, i would doubt that kid made changes to the ecu.
Even if he changed the injector coding it will still run but like a bag of shit
To clear codes you go into engine it has code info you hit "y" yes and when you want out it asks "do you want to clear codes" "y" yes "n" no, its so easy

Hope this helps Alan.