Psn account questions

hey, im wondering is it possible to add games to ones psn account on an app through the use of a cd key. im trying to sell a cd key on craigslist and this way they can just add the game to their account and not claim its been used already.

If you have a code such as from a PSN card or a game download code, you can enter the code and download using the Official PlayStation App on iOS/Android. If the code has been used, then you can't add anything.

thats all i need to know, thanks.