LG G4 5.1 change all volumes at once and stop apps from raising?

[daved31415]

Looking for help with two things, preferably without a third party app. Using Android 5.1 on a Verizon LG G4, I'd like to have the come buttons change a volumes at once ... I use the buttons and the priority button shown after pulling down the top bar but it both cases I'm always checking the separate volumes to be sure they changed.... Number two is I'd like to be able to lock the volume silent.... SO many times now I've had an app raise the volume, especially videos.... I will check that l are at minimum and then video starts to play with volume. Has been embarrassing a few times in quiet settings.