Important: You can't restore a backup from a higher Android version onto a phone running a lower Android version.
Requirements are for individual Actions, while Gates apply to all of them.
In Actions, you can define the activities to perform once you double-tap.
You can create some very useful shortcuts if you take some time to explore.
I found TapTap Flashlight very useful since when I usually need my flashlight — for a quick visit to the bathroom at night, for example — I have no time to unlock my device and fondle through menus.
Those considerations aside, Tap, Tap reportedly works well on a variety of Android devices.