A couple of days ago, we covered how there was a way to dual boot between iOS 6 and iOS 7 on iPhones and iPads. Winocm has released a toolset that enables those interested to run different versions of the same software on their iOS device. Keep in mind that hacking your iOS device this way does require some knowledge of hacking. You should understand the risks before trying it or use a spare device just to be safe.
As it is mentioned on Github, there are no warranties with this method. But if you want to learn hacking, this is a good way to get started.