iPhone Jailbreak OR Downgrade Locked iPhone 4 & iOS6

[Baklava]

Hello all,

a friend of mine has an iPhone 4 with sim-lock and iOS6 installed. Is there any way to jailbreak & unlock it without a valid sim-card? If not, he would like to downgrade to 5.1.1 if possible.

Thanks for any advise

 

[dhlizard]

Only if he saved the 5.1.1 hashes