How do I lock iPhone 5 in landscape mode?
Apparently you can!

If you want to try this out for yourself, here is the navigation to get to the setting:


Enabling AssistiveTouch: 
Settings App>General>Scroll Down to Accessibility>Scroll Down to AssistiveTouch '
Toggle on AssistiveTouch.


Switching to Landscape:


Lock the device in portrait mode
Press Floating Square>Device>Rotate Screen>Left/Right


http://www.todaysiphone.com/2011/10/tips-tricks-lock-iphone-orientation-in-landscape/ ......................