In iOS 11.2 application I have noticed an unusual behaviour (opening forcefully closed apps, sometimes shows the previously visible view and redirect to the launch screen), I don't know whether it is bug with OS or something else but it can sometime appear in Google app also.
You can find the related video in below link. https://s3.amazonaws.com/uploads.hipchat.com/37040/3355524/7K3EL8N5X55tN8p/ScreenRecording_12-13-2017%2013%3A23.MP4.
Please help me to figure it out whether it is a feature or bug.
In my opinion, it's rather a bug or just normal behaviour, not a feature. There is some time before the app is dropped from the RAM, used to save some data, e.g. in
appWillTerminate, etc., but it should not make an effect like you have observed. From the second hand, maybe device holds the image of how app looks like before the rage quit and shows it up, then freshly opens the app.