I tried updating my iPhone 4 to iOS 7 beta, without developers account, using restore + shift on itunes and clicking my downloaded IOS 7 firmware. This failed at a certain part, it said error 1934 or something, at that point my phone was still working, then I tried again and it became stuck in recovery mode. I tried different tutorials but I just can't get it working again, please help!
Iphone stuck in recovery mode after updating to IOS 7 beta?
Apple is preventing you from installing the beta without registering your UDID. Even if you can get around that like before, it's dangerous to install it without a UDID registration because Apple has actually been disabling devices for running unreleased software on unregistered devices. I registered my 4S on http://www.instantudid.com/ and I haven't had any issues at all.
Never install a beta without registering your UDID first as Apple could deactivate the device at any time. You can register UDIDs with http://ios6udidactivations.com
Hold power + home button until you get iTunes restore, or use a program like iReb or redsn0w to fix boot loop. You have to do a clear restore to 6.1.3 then setup as new phone then shift+update will bypass registration. Good luck