The recent apps feature in Lollipop appears to behave differently from previous versions. First of all, as you noticed, the button to clear all recent apps is gone.
how-to-disable-recent-apps-button-in-android-programmatically
Even disabling the system battery restrictions does not save the app from being killed. ... On Android 11 Samsung will prevent apps work in background by default ... or in a group by selecting them then tapping the big Save power button. Apps .... Sep 27, 2015 — Go to the list of recent apps, find the app you're looking for, and tap on it. (In iOS this is done by tapping the Home button twice; in Android by ... 3925e8d270
android disable recent apps button programmatically