My client wants to make a small game for iOS and Android that rewards users when their friends accept their invites through Facebook.
I've read several questions and solutions I found on this site about getting the "from" and "to" fields from the facebook request.
However, on MOBILE, when a new user clicks a notification on FB apps, he/she will be redirected to the appstore page and need to download the app first. So after downloading, when new user opens and logs in to the app, how can I know who is the sender so that I can reward him?