Is there a way to get the currently running application (package) for all available OS?

Question

I know there are too many questions already addressed in this topic, but which are not supported in all OS / devices

Question

• Is there a way to get the current running application (package) for all available OS ?
• How does AppLock work (how does it detect application launch)?

What I tried (but failed)

• How to determine if an Android application is running? - Google is disabled in Android L.
• How to use UsageStatsManager? - android.permission.GET_TASKSdeprived.
• How to make my application the owner of the device? - Unable to execute this command programmatically.
• Knox Standard

What I want

• . ( , AppLock )
• , .
• , , /.
• //

Answer 1

2 , , , , .

1) "launcher". , . , , .

2) "" . . "", , , . - , .., ( , , " ", , , ( ).

!