Got an iPhone 3G, 3GS or iPod touch 2/3G? Want in on the iOS4 action right now, but you’re not a developer? Well you’re in luck! Apple’s latest iOS4 release, the Golden Master (GM), doesn’t require a developer account to activate and is ‘freely’ available for download if you know where to look. [Update: The iOS4 update that Apple released on Monday 21st is freely available and can be jailbroken using this method]

But what is the GM? Don’t I have to wait till Apple releases iOS4 on June 21st? As you already know, iOS4 has been in the works for some time now, released to developers in beta form so they could perfect their apps ahead of time, ready for the release of the new iOS. The GM is the final step in the beta process, and essentially what Apple is denoting with that moniker is that iOS4 is feature complete. It’s the same thing for instance, when a Microsoft desktop OS is said to have gone gold, or RTM, which stands for Release to Manufacturing; it’s ready for printing onto DVDs. So the GM of iOS4 is what you’re going to get if you wait until the 21st of June like everyone else, bar any unforeseen killer bugs that haven’t been ironed out in the beta process (highly unlikely).

So what do you get from iOS4 and why would you want to update? Well on the 3GS you get all the trimmings, multitasking (of some sort), home screen wallpapers, folders, Game Center (only available in the GM not the public iOS4 release), the works. On the iPhone 3G you get basically everything but multitasking and home screen wallpaper. Perhaps for a 3G user then, the emphasis to update is not as great, because let’s be honest it’s all about the home screen wallpapers right?

Well, hold your horses iPhone 3Gers. You too can get in on the funky wallpapering action, and enable multitasking, all with a simple text edit. But for that you’ll need to jailbreak iOS4 on your device, which is both possible and easy, right now.

There are two small snags before you jump the gun. This jailbreak is only available for the iPhone 3G currently, but if you’re just after a stock update to iOS4 you’re good to go with an iPhone 3GS and iPod touch. The second small snag is that you’ll need iTunes 9.2 beta to sync iOS4, which is currently only available on Mac. So for all you PC users, I’m afraid you’re going to be left out in the cold until a windows version of iTunes 9.2 comes along. now available on all platforms ready for iOS4. iTunes 9.2 is now available for both Mac and Windows, so if you’re not using Linux, you should be good to go.

OK, I’m on-board, what do I need?

How to Update and Jailbreak your iPhone 3G using a Mac

Firstly, to update to iOS4, download the applicable iOS4 .IPSW (iPhone Software) file for your iDevice and you’ll need iTunes 9.2 beta for Mac, which are both available from here. which are both available directly from Apple, iTunes and How to update by Apple.

PSA: Updating to iOS4 without modification first, WILL UPGRADE YOUR BASEBAND. If you intend to use yellowsn0w or other carrier unlock DO NOT UPDATE TO iOS4 with this method. There are also issues with iBooks currently, as some users are noticing that they cannot download and read books in iBooks after jailbreaking with redsn0w.

[Update: The iPhone Dev team have put out a new redsn0w release that should be able to hacktivate the upgraded baseband]

Whilst they’re downloading, hook your iDevice up to your computer and make a proper backup, because upgrading from 3.x to 4.0 is going to require a full restore. So if you want all your game saves etc, you’re going to have to restore it all back with iTunes once you’re done updating.

OK, backup – check!

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Next install iTunes 9.2 and ensure it runs fine (it should run fine as long as you’re running Leopard or Snow Leopard) – check!

As a precaution, go into the System Preferences (Settings) on your iPhone and disable any SIM Pin lock you might have employed, before proceeding.

Plug your iDevice in and select it in iTunes. Then shift-click (Windows) / option-click (Mac) the restore button in iTunes and point it to the applicable iOS4GM .IPSW file that you downloaded earlier. Make sure it’s the right one for your device before you proceed. Select ‘Check for updates’ and then follow the instructions shown by iTunes or here.

Click OK to restore. It’ll take about 7-10 minutes to get a usable state. Once it’s installed it’ll appear as a freshly wiped iDevice in iTunes, which from there you can restore your information, music, apps etc. If you’ve got an iPhone 3G and you want to jailbreak, hold off on restoring your content onto your iPhone until you’ve jailbroken it, just incase you need to restore should something go wrong.

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Everything running alright? Liking the look of iOS4, but you’re missing two vital ingredients? Let’s set it free, it’s jailbreaking time!

Again, this is where you step ahead of everyone else, because you’re going to be using a beta version of redsn0w. The iPhone dev team has promised an official jailbreak sometime this month, and if early indications are anything to go by, we should see it pretty soon. But just like Apple, the iPhone dev team has been letting jailbreak app developers get a leg-up, before the official release of an iOS4 jailbreak. Using the redsn0w 0.9.5 beta it is possible right now to jailbreak iOS4GM for the iPhone 3G using the ‘point it at the earlier firmware’ trick. With that I mean, by pointing redsn0w at iOS4b4 you can jailbreak an iPhone 3G running iOS4GM.

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The jailbreak itself is easy, following the instructions from redsn0w just like jailbreaking the old iPhone OS3:

Download the redns0w 0.9.5 beta from here (Windows) / here (Mac) and find yourself the iPhone 3G iOS4b4 .iPSW file.

Plug your device into your computer and turn it off fully using the slide to turn off rather than simply holding down the power button.

Close iTunes if it’s open, fire up redsn0w and point it at the iPhone 3G iOS4b4 .IPSW file you downloaded earlier. Click through the prompts till the next stage.

Redsn0w will now guide you through getting your iPhone into DFU mode and the automated jailbreak.

Once it’s all finished your iPhone 3G will reboot. Check that you’re receiving cell signal, if you’re not you’ll have to restore and then re-jailbreak, but it’s unlikely at this stage.

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Next open Cydia, which is just a blank, white icon for now. It’ll do it’s re-ordering then respring your device. Open Cydia again, and go to sources and input Saurik’s default repo as a new source:

http://apt.saurik.com/cydia-3.7

It’ll then download the default sources and ask you to upgrade Cydia. After all that, you’re set and Cydia will have it’s usual brown logo. Congratulations you now have a jailbroken, iPhone 3G running iOS4.

But wait there’s more! Fancy trying out multitasking and home screen wallpapers on your iPhone 3G, Apple be damned? Read on.

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So as it turns out, your ability to use multitasking and wallpaper in iOS4 is controlled by a simple key entry into a plist file in the Springboard app. To enable the features all you need to do is add a quick line of code into the plist file and reboot your device.

Now if you’re not comfortable messing around with plist files, which are essentially text files that act a bit like the Windows Registry, then I suggest you stop now and save yourself some time and effort. For those of you in for the full hog, here we go.

I’m going to describe how to do this using iPhone Explorer. Most people seem to use SSH to get files to and from their iPhone, but I prefer the ease of use and zero hassle that iPhone Explorer provides.

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First off, you’ll need to download a couple of great and free tools iPhone explorer (Windows and Mac) and Text Wrangler (Mac) or Plist Editor (Windows).

Next, plug your iPhone 3G into your computer, fire up iPhone Explorer and navigate to this folder:

/System/Library/CoreServices/SpringBoard.app/

Find and copy the .plist file N82AP.plist to your computer. Make a backup of this file and then open it with Text Wrangler/Plist Editor. Make two small entries into the .plist file under the capabilities key:

<key>multitasking</key> <true/> <key>homescreen-wallpaper</key> <true/>

Which should look like this:

Save the file with Text Wrangler/Plist Editor and then copy the edited file back to your iPhone into the same folder overwriting the original:

/System/Library/CoreServices/SpringBoard.app/

Unplug your iPhone from your computer and reboot it (turn it off and on again or reset it) to complete the change.

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Bobs your Uncle, you can now change your home screen wallpaper and multitask. For what it’s worth I’ve been running it for a couple of hours now and it seems to work fine. I would even go as far as to say it’s faster than 3.1.3 was, but maybe that’s my imagination.

If for any reason you want to reverse the process, simply go back and replace the N82AP.plist file with the original and reboot. Simple.

[UPDATE] Apple has now released iTunes 9.2 for both Mac and Windows, so iOS4 can now sync with both platforms. After some experimenting with iOS4 updated apps, I can safely say that for the most part ‘multitasking’ works as advertised, but the iPhone 3G is a lot faster if you have home screen wallpaper disabled. I’ve also included instructions for using a Windows PC.

[UPDATE 2] The iPhone dev team have released a cloud based jailbreak for iOS4 devices at Jailbreakme.com – check out the details here.

[Thanks to Redmond Pie]