You can jailbreak iOS 4.3.5 on the iPHone 4, 3GS, iPad 1 and iPod touch 3rd and 4th gen with RedSn0w. Sorry, no iPad 2. Also, it’s a tethered jailbreak (read about managing a device with a tethered jb), so we don’t recommend using it on an iPhone. If for any reason you have to power it off, you will be without a phone until you can get back to your computer.
Here’s how to do it:
1) Download both iOS 4.3.5 and 4.3.4. (the easiest way to find firmware you need is to use an ipsw downloader [Mac and PC]). We suggest keeping a firmware folder and calling it Jailbreak. This will house firmware you intend to jailbreak and keep it in a place that’s simple to find.
2) Now, download Redsn0w 0.9.8b4 (via Dev-Team Blog)
3) Make sure you are using iTunes 10.4 (via Apple)
4) Launch RedSn0w.
5) Look for iOS 4.3.4 firmware. Do NOT use the 4.3.5 firmware. Now direct RedSn0w to 4.3.4.
6) Redsn0w will identify the iPSW.
7) Hit next, and only check off “Install Cydia.” Now hit next again.
8) RedSn0w will give you some instructions. You must turn off your iOS device and have it plugged in. Make sure to read the onscreen instructions carefully. Redsn0w walks you through the process.
9) You will now have to put your iOS device in DFU mode. This is tricky the first time, but you have to do this correctly. Again, RedSn0w will walk you through exactly how to do this. Here’s a video showing it as well:
10) Once you have done that, RedSn0w will begin the jailbreak. Sit back and wait, or get a drink. Just let RedSn0w (and your computer) do their thing. It doesn’t take too long.
11) Your device should boot back up and you now have a jailbroken device. It’s tethered, so EVERY time you want to reboot, you will need to plug in and of the DFU mode thing with “Install Cydia” selected.