I want to show players that they have received an apprequest from their friends.
I can do this already with this code:
FB.API("/me/apprequests", HttpMethod.GET, ResponseCallBack);
You should not use apprequests for realtime stuff, better use Websockets (Node.js + Socket.io) or Firebase (Realtime Database) for those kind of things. Apprequests are more like "fire and forget" notifications.