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?
You could use iTunes to RESTORE your iPhone to it's original version of iOS.
BUT, it's a new iPhone 5, so the iOS version that came Factory PRE-INSTALLED is the latest version.So, you are beat, until the Black Hat Hackers can find a way around iOS 6.1.3.
TIP: Just so you know, "I can't afford it" is no excuse to PIRATE Apps and Media files. If your parents knew that you plan to steal stuff, they likely would NOT allow you to Jail Break your new iPhone, and, VOID the Warranty. I'm telling your Mom…
There is a special button "Restore" in iTunes. Good luck!
You cant, if you did not jailbreak and save those shsh blobs