iOS 4.2.8 is available for CDMA iPhone 4 users on Verizon, with iOS 4.3.3 for GSM iPhone 4, iPad 2, iPad, iPod touch 3G/4G to fix the iOS location tracking bug. To update to iOS 4.2.8, connect your iPhone 4 with your computer via USB and start iTunes. You should see a message prompt. Click on “Download and Install” (Mac OS X) or “Download and Update” (Windows) button to get the new firmware 4.2.8.
Following methid will guide you about how to jailbreak Apple TV with Seas0nPass jailbreak tool, which can create custom firmware like PwnageTool. Currently the jailbreak for the 4.2 (iOS 4.3) software is ‘tethered’. A tethered jailbreak requires the AppleTV to be connected to a computer for a brief moment during startup. Seas0nPass makes this as easy as possible, but do not proceed unless you are comfortable with this process.