Some things to note...
Settings > Apps > Recently Opened
The Forced Stop option is shown there if the app is currently open in the background.
Use the function on the Navagation Bar and close all the apps that it shows there.
Then reopen the Recently Opened apps function and the 'Force Stop' option is gone from all them apps.
So open an app (I opened Total Commander app), then close or exit that app , not with the RCU exit button but find how to close the app from the apps menus.
Then reopen the Recently Opened apps and the Force Stop is showing there on the Commander app.... so that is telling me that the app never closed , so I use the Force Stop and then open the Navigation Bar function and there is the Total Commander showing still as open.
Another thing too is if i use the Home button 3 or 4 times then I get a message that says it closed 3 apps... but according to which apps have the Force Stop option showing in Recently Opened or show in the Navigation Bar setting and they show 5 or 6 or 7 apps, while in reality only 3 were open.
SNAFU
i do not think these functions are working 100% correctly as far as showing which are actually currently opened.
Its a kurfluffohhh
So in conclusion, if you follow my 'testing',... I do not think either of these methods are telling us if indeed an app is actually closed or open.
Either will definitely close an app or all apps, but to positively know for sure if an app is open is not, it is not possible thru either of these methods or combined the two either.