Hi,
on Android 4 and higher, you can still close Firefox or any other app from the app switch screen.
- Ice Cream Sandwich: long press on the home button.
- Jelly Bean: tap on the app switch button
.
If you need the menu item back, you can install an add-on like the QuitNow add-on to do that. Here's how to install an add-on to add Quit back.
