Why is ad still briefly playing after a restart?
iOS has a feature to make "unpausing" apps seem faster when they are not in memory anymore. Your device keeps a screenshot of your app and if it has to be purged from memory (put on pause) it will show the screenshot until the app is ready. 
This usually works very well but can look unexpected when you force quit the app which leads to it not taking off at the same point but showing the initial screen again.