The iPhone Dev-Team is back! They have just released a test version of redsn0w 0.9.5 (download link) (Mac only for now) to jailbreak the latest iPhone OS 4 Beta. This release is targeted towards developers only to help them upgrade their existing app on Cydia for this upcoming latest firmware .
Note: This release WILL NOT help you hacktivate or unlock your phone. You’ll need a registered UDID with Apple to get past the activated process. Therefore, DO NOT update to iPhone OS 4 Beta if you rely on an unlock, as upgrading will upgrade your baseband which will leave you locked.
The following step by step guide will help you jailbreak your iPhone 3G ONLY (for now) on iPhone OS 4 Beta.
Step 1: Download iPhone OS 4 Beta for iPhone 3G.
Step 2: Update to this latest firmware file: iPhone1,2_4.0_8A230m_Restore.ipsw
Step 3: Start redsn0w 0.9.5 and point it to the original iPhone OS 4 Beta firmware for iPhone 3G to proceed.
Step 4: Now select “Install Cydia” and click “Next”.
Step 5: Now make sure your device is both OFF and PLUGGED IN to the computer before you click “Next”.
Step 6: Connect your device in recovery mode by pressing the Power and buttons continuously.
At this stage you will be presented with a screen where you will have to quickly hold “Power” button and then while holding the “Power” button, you will now have to hold “Home” button too. Now after few seconds release “Power” button but keep holding “Home” button until installation begins.
Step 7: Sit back and enjoy while redsn0w will do all the rest for you. Once done, your iPhone 3G will restart automatically and you will find it jailbroken with iPhone firmware version 4.0.
You will now notice that Cydia has a blank white icon. You’ll also notice that Cydia has no sources. Go to the Sources panel and add http://apt.saurik.com/cydia-3.7 repo. Now restart your phone and you should see the regular standard Cydia logo now.
How-to Enable Multitasking:
Once done, you can now enable multitasking on iPhone 3G, OS 4 by simply editing a N82AP.plist file as mentioned here. Open the said .plist file and change the multitasking key to = TRUE. If the is not there, add it and you’ll be done.