You should make it so that once a player does a thing you make a global value for the GJ trophy and save it via the INI
If the player hasn't logged in but did the thing it should be saved in the INI regardless of being logged in or not
and once the player logs in they should get the trophy without having to do said thing again

For logging in saving and not having to retype it again you should make a global string for the Username and Token and then once the player types their info, the info should be saved via global string
and then you can use that global string to save it in the INI