Few hours are left for final iPhone OS 4.0 release at WWDC 2010 and good news for iPhone 3G & 3GS jailbreakers & unlockers is that iPhone Dev team is ready with their jailbreaking tools for iPhone Firmware 4.0 also with tools to unlock iPhone 3G/3GS 4.0.
Here is simple guide for those Users who will be first time upgrading their iPhone 3G/3GS to firmware 4.0. The guide is applicable for Upgrading iPhone from any OS version below 4.0 (3.0,3.1.2 or 3.1.3) to 4.0 and also for iPod Touch. Please note in order to upgrade iPhone to firmware 4.0 you must have latest version of iTunes software installed.
How to Update/Upgrade iPhone 3G/3GS to 4.0 firmware
1. Connect your iPhone 3G/3GS to PC
2. Start iTunes
3. Select your iPhone under Devices in the Source List on the left.
4. In the iPhone Summary pane, click Check for Update.
5. Click Download and Install. Do not disconnect your iPhone until the update has finished
That’s it, Once update is finished your will have iPhone 3G/3GS running latest iPhone OS 4.0
For Jailbreakers & Unlockers
You can jailbreak iPhone 4.0 OS with redsn0w 9.5.0 or download Pwnagetool 4.0 or by grabbing iPhone 4.0 custom firmware file from internet. The unofficial Blacksn0w tool can unlock iPhone 4.0 on iPhone 3GS.
If you have mistakenly upgraded your iPhone 3G/3GS to 4.0 OS then follow our guide to downgrade iPhone 4.0 to 3.1.2 or 3.1.3.