How to prevent an app from running in the background at all?

Nikoyay

I have an app that I want to only run when I open it, and it should stop running the moment I close it.
Is it enough to disable "Allow background usage" from its battery settings? Why is the "Force stop" button active then, does that mean the app is still running?
I have also disabled "Background data" under its Mobile data usage permissions, but does that mean it can still use WiFi in the background?
Is there another option I'm missing?

Byku

From my experience:

disabling running in the background prevents an app from running a foreground process (what you see under active apps) when closed
an app can still start a foreground process after reboot even when the above is set
an app can still make connections in the background but these can be more sparse although it's completely dependent on the app how it will behave, I've had apps continuously spamming connections regardless
similar story with restricting background mobile data plus it does not affect wifi
force stop works well usually but not to as well as disabling the app, I don't know what are the exact conditions for a force stopped app to restart

Skorp

Those are the options available to the system to manage the background usage of the app. A couple of other options that you might explore would be:

Disabling the app when you don't need to use it.
Putting it in Private Space, as when Private Space is locked it does not run and apps within it do not run.

Nikoyay

Skorp Thank you, I'll try the private space approach.