What is the latest version of the iphone is untethered jailbreakable?

I have an iphone 3gs version 6.1.3 but i can't find an untethered jailbreak for that version so i'm gonna downgrade it so which latest version has an available untethered jailbreak?

Added (1). I messed up that question lol should have been asked: which of the latest versions of the iphone 3gs is unthered jailbreakable?

Last week, a hacking team called UnthreadedJB appeared out of nowhere to release an untethered jailbreak for older iPhones, iPads and iPod touches running iOS 5.1.1 or earlier. The team behind the jailbreak has now gone onto claim that they have a working untethered jailbreak for iOS 6.1.3 and iOS 6.1.4 running on newer devices like the iPhone 5, iPhone 4S etc. This is newsworthy, since evasi0n doesn't work on iOS 6.1.3 and above.