Open an app with task extention

hi i need help
I am making a Clock app and almost all the work is done except for one part that is related to alarms. I want the application to open after exiting the program and for example after a few seconds.
I used Activity Starter but it doesn’t work when working in the background.
I also wrote some other parts that all work properly, such as notification and alarm, but the activity starter does not work.
Can you help me, I really need this.

As already said in PM

generally use the itoo extension, the background tasks extension is discontinued

my alarmmanager extension is able to start your app after a few seconds

see the restrictions in the documentation