If you want to know yes I want to jailbreak my phone. This is a temporary solution for me as I don't have a job yet and I am not old enough to own a credit card.
How to downgrade my iPhone 5 from iOS 6.1.3 to iOS 6.1.2?
There is a special button "Restore" in iTunes. Good luck!
You cant, if you did not jailbreak and save those shsh blobs