To see what other apps you have open hold down the alt key and then push the back key. You can then let go of the back key to scroll through the apps but keep the alt key held down. There are something like 5 apps you can't close such as the home screen. Also when you are done with an app clicking on the red hang up key does not close the app it just kinda puts it in standby mode. When you are done with an app click the menu key and select close or exit to be sure the app has closed.
I held down the ALT key and pressed the back(del) key. Nothing came up