You can find that in Battery Sense. Look at the app list and then select an app and see if it's allowed to run in the background or not. Some apps don't give the option to be disabled though.
Heck! I can't find battery sense neither in app list nor in settings. My phone runs on DP and Cortana is enabled using region as the US. Not sure if Cortana hides it or is there still a way to find and manage background tasks?
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