GcmListenerService when running in background different

I've followed this tutorial to create a new GCM Listener service: http://www.appifiedtech.net/2015/08/01/android-gcm-push-notification-example/

The code for the listener service:

@Override
public void onMessageReceived(String from, Bundle data) {
    super.onMessageReceived(from, data);
    String msg = data.getString("message");
    Log.d(TAG,"GCM Message received is "+msg);
    // Notifying to user code goes here
    notifyUser(getApplicationContext(),msg);
}

public void notifyUser(Context context,String data){
    Intent intent = new Intent(context, NotificationActivity.class);
    intent.putExtra("data", data);
    intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK |
            Intent.FLAG_ACTIVITY_CLEAR_TASK);
    PendingIntent pendingIntent = PendingIntent.getActivity(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
    NotificationCompat.Builder builder = new NotificationCompat.Builder(context);
    builder.setSmallIcon(R.mipmap.ic_launcher);
    builder.setAutoCancel(true);
    builder.setContentTitle("New Notification");
    builder.setContentIntent(pendingIntent);
    builder.setContentText(data);
    NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
    Uri uri= RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
    builder.setSound(uri);
    notificationManager.notify(countNotification++, builder.build());
    Log.v(TAG,"count "+countNotification);
}

When the app is running (foreground), this works fine and launches the Notification Activity as it should.

However, when it's running in background, I get the notification but the title and body are as defined in my server sender application, and tapping on it takes me to the Main Activity.

1. This essentially means that when it's running in the background something else handles the notification? Is there another handler I should implement to be able to manage that notification and send the user to the correct activity?

2. The screen does not wake when I receive this notification, nor does an LED light up on the phone as notifications from other applications do. How do you manage that?

(permissions, services and receiver are defined in the manifest as described in the tutorial)

1. In problem regarding when your apps running in the background something else handles the notification?

This SO question can help you in answering your question regarding the GCM Listener Service

2. In the problem regarding to the screen that doesn't wake when you receive notification.

Use ACQUIRE_CAUSES_WAKEUP

Normal wake locks don't actually turn on the illumination. Instead, they cause the illumination to remain on once it turns on (e.g. from user activity). This flag will force the screen and/or keyboard to turn on immediately, when the WakeLock is acquired. A typical use would be for notifications which are important for the user to see immediately.

You can visit this SO question in how to use it.