How to get iOS7 on my iPhone 3GS?

I found a site with a Jailbreak that is a copy of iOS7 but is not genuine. Ideally I would want to Jailbreak/hack my iPhone "tricking" it into thinking it's an iPhone 4 or higher. Then, when iTunes reads it as an iPhone 4 etc I can update it to Apple's genuine iOS7. Is this possible?

That hardware is too outdated to run iOS 7.