Dev-Team has release RedSn0w 0.9.6b4 to jailbreak iOS 4.2.1 on iPhone 4, 3GS, 3G, iPod touch 4G, 3G, 2G and iPad. RedSn0w 0.9.6b4 jailbreaks iOS 4.2.1 with working Cydia and MobileSubstrate. Step-by-step instructions on how to jailbreak iOS 4.2 with RedSn0w 0.9.6b4 after the jump…