I say they are undocumented because I have not found any reference to them in the sensation user manual or on any of several android forums. All these were found and documented using ICS 4.03 so I don't know it they work on other versions, but it won't hurt to try.
The first is "Safe Mode" this is like safe mode on a windows PC. It loads the OS without loading any low level apps and allows one to load apps one at a time to see which is causing a problem.
Power off -> power on -> when the htc logo appears hold the volume down key down until the device completely boots. There will be a "Safe Mode" notification in the lower left of the screen.
The second is power on without touching the power on button. With the screen off touch the home screen icon and swipe to the search icon - and voila the screen comes on.
The Third is taking a screenshot in a new way. The normal method of taking a screenshot is to depress the power button then hit the home screen icon. The hidden function is to tap the search icon and swipe to the home screen icon - and voila a new screenshot.
The first is "Safe Mode" this is like safe mode on a windows PC. It loads the OS without loading any low level apps and allows one to load apps one at a time to see which is causing a problem.
Power off -> power on -> when the htc logo appears hold the volume down key down until the device completely boots. There will be a "Safe Mode" notification in the lower left of the screen.
The second is power on without touching the power on button. With the screen off touch the home screen icon and swipe to the search icon - and voila the screen comes on.
The Third is taking a screenshot in a new way. The normal method of taking a screenshot is to depress the power button then hit the home screen icon. The hidden function is to tap the search icon and swipe to the home screen icon - and voila a new screenshot.