I notice this one little problem, the thread is moving too fast I'm not sure if it's covered but if it's covered I apologize for my ignorance.

If you hold the menu button quickly you can clear all the opened apps. Which I think is good because you can give more space to the ram. But what I noticed is for example Facebook Messenger and Kakao, once I clear them and somebody tries to message me, I have to manually open Kakao only then I can see the notifications.

But for Twitter and Instagram, even though they are not running in the background, when someone tweets or comment on my picture, I receive notifications instantly, what's wrong?