How can i upgrade a 2g iphone to the latest firmware. The iphone is jailbroken and unlock too.?

I hаνе іt nοt through ATT. Cаn ѕοmе one guide mе οn hοw tο upgrade thіѕ iphone? lіkе іѕ ѕаіd іѕ a 2g iphone unlocked аnd jailbroken аѕ well. Thanks

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