how does whatsapp service gets restarted even if i force stop app?

Question

I am running whatsapp (we could call it appX from now on) in device A. I go to manage applications -> force close so appX gets closed and i no longer see appX as running ser

Answer 1

Starting from Android 3.1 (API 12), if an application is force-stopped it will not restart until the user manually runs the app again.

This will happen even if the app contains a Service or an active BroadcastReceiver.

You can find the official documentation here.