How can one access hidden apps on the Samsung Galaxy Tab2 7.0?
These apps are not hidden. They were not meant to be launched.
The example you mention - Phase Beam - is a live wallpaper. To use it long-press on your homescreen and select live wallpaper. 
There're many others that can't be accessed by the end user. They're meant to be used by another. Usually to provide a feature in a plugin form.