Okay so I managed to downgrade my iOS 6 to 4.2.1 WITH a broken power button using redsn0w's DFU IPSW (creating DFU IPSW with your current version) so I can enter DFU without power button. Now my question: can I do it with the same procedure but this time, jailbreaking it (untethered) with version 4.2.1? So it will be most likely customizing another DFU IPSW (this time it's 4.2.1) restore it to iTunes, DFU mode then jailbreaking with either redsn0w or Greenpoison??? (which is better?) I also remember that someone told me to check the "set host to cydia" since my version was iOS 4.