I'm looking to downgrade my iPhone 3GS (currently has OS 4.3.3) to OS 3.1.2 or OS 3.1.3, I already have the OS 3.1.2 ipsw. However, after 7 hours of searching for a way, I cannot find a (working) way to revert back using Linux, as it can have neither iTunes nor any of the jailbreaking software that can allegedly accomplish this, and it's a bit tiresome.

If you can give me assistance, that may require further communication, you can email me at kristen111695(at)yahoo(dot)com where I will redirect you to my primary email.

Thank you in advance to anyone who can help!
Also, feel free to ask for additional details if what I have provided is insufficient