@terryzai1403

4.3.5 is the latest version of the iOS 4.x family. You should use 4.3.5. Firmware older than what is posted at http://www.felixbruns.de/iPod/firmware/ , usually will not pass validation with Apple when you try and restore to them.

Unfortunately, I believe the only jailbreak available for 4.3.5 is a tethered one at the moment.

If you can hold off for a while, iOS 5 *should* be released soon - Possibly next month. It might be less stressful just to hold off till then.