How to install iOS 7 Beta version in your iDevice without having a Dev account or UDID
Step 1: Update Your IDevice to the Lastest IOS
The first thing you need is to have your iDevice in the last version of iOS. For iPhone 5 is 6.1.4 and for other devices is 6.1.3 Make sure your device is restore in that iOS, I mean that your iDevice must be completely restore, with no music, no apps, etc. completely blank
Step 2: Download IOS 7 Beta
Go to the link:
And download iOS 7 Beta 3 for your device
Step 3: Restore to IOS 7
Connect your device via USB and open iTunes, on RESTORE hit the SHIFT and left mouse click buttons down together, this allow you to manually select the iOS you just downloaded. Select the iOS 7 for your device and wait for the restore.
Step 4: Enjoy IOS 7
Enjoy your iDevice with the iOS 7 beta before anyone. You can update your device with the next beta version in Settings/General/Software Update without any problem. Remember that is a beta version and you may experience some issues and bugs.