If you want to upgrade to iOS 5 but you have locked iPhone unit (aside from 4S), you might want to consider the ability to preserve your baseband to be able to unlock. UltraSn0w (V 1.2.4) unlock was just recently released for iPhone 4/3GS/3G that runs iOS 5. Here is the list of basebands that are compatible for unlocking:

iPhone 3GS: 4.26.08, 05.11.07, 05.12.01, 05.13.04, 06.15.00

iPhone 4: 01.59.00

You can follow the procedure in updating iOS 5 without updating your baseband for Windows and Mac in our previous posts.

In order to unlock your iDevice, you need to jailbreak first since it needs Cydia to download the UltraSn0w 1.2.4 package. Make sure that your baseband is listed above or else the unlocking process will not do.

A release note from the Dev Team is posted for users of iPhone 3GS and other possible baseband downgrades for some situations:

Note: there’s a special “trick” that iPhone3GS owners with baseband 06.15 need for iOS5. During the new setup screens you see when you start iOS5 for the first time, you’ll be asked about Location Services. Be sure to select “Disable Location Services” when asked! Later on in the setup, you’ll have the chance to turn on Location Services again when asked if you want to use “Find my iPhone”. It’s fine to turn it back on at that point, if that’s your desire (or you can always go in and enable it in Settings.app).

Also, some iPhone3GS users with the 06.15 baseband may have tried to install iOS5 using a stock IPSW (even though you should never ever try to use a stock IPSW if you’re an ultrasn0w unlocker). If you did try this, your baseband is probably in an inconsistent state, and you’ll need to reflash the 06.15 baseband again (using redsn0w). Be very careful if you use redsn0w to reflash the iPad baseband — don’t interrupt the process! And please avoid using stock IPSWs in the future  Unlockers should never go near stock IPSWs.

Many people are confused about how jailbreaking differs from unlocking, especially the new users of iPhones. While many of the jailbreaking community knew the difference, this article is highly dedicated to people who have doubts on how jailbreaking differs from unlocking.

What is jailbreaking?

Jailbreaking is the process which modifies your iOS firmware which then allows unsigned code to run and gain access to files in your iPhone which was previously prevented by Apple. After the jailbreak is successful in your iPhone (also for other iDevices), an unofficial application installer called “Cydia” will now be added in your springboard which will allow users to install cracked apps from the App Store and third-party applications which are not available in the official App Store.

To install cracked App Store apps for free, you need to download first Installous through Cydia. I do not recommend this but it’s worth telling it to everyone. After all, your iPhone is yours. Cydia also provides non-App Store apps that enhance your iPhone called “tweaks” like customization of the themes, lockscreen, ringtones and many more.

Once should not be afraid in jailbreaking their iPhone since the process can be easily reversed by restoring in iTunes in case things may not work as you expected. But trust me, once you have tried jailbreaking your iPhone, you’ll always want to have it jailbroken.

What is iPhone unlocking?

iPhone unlocking is the modification of your device’s modem which allows you to use any carrier SIM cards. The most common method of unlocking is through the use of software but is only limited to some basebands. Some software also requires you to jailbreak first before you can unlock like the UltraSn0w which was developed by the Dev Team.

Gevey SIM is also another process of unlocking your iPhone. You can read more about the details in my previous post.

Unlocking an iPhone is the process of removing SIM (Subscribers Identity Module) restrictions thereby giving you the chance to use your iPhone in any carrier. This is the main reason why do you need to unlock your iPhone. If you are satisfied with your carrier right now and is not planning to bring your phone abroad, then there is no need to unlock. Software unlock or hardware unlock are the two types of unlocking processes. Hardware unlocking can be done through the modification of the device and is not highly recommended.

Software unlocking can be done easily and is safer to use since iTunes can restore your iPhone back in case something will happen unexpectedly. This method is provided freely by the DevTeam, the premier organization of iPhone hackers who are constantly developing processes to unlock or jailbreak any Apple device.

There are two things to consider before you unlock your iPhone. First, make sure that the carrier you want to use supports the iPhone technology. Second, you need to know your FirmWare version and modem version (or baseband) if it is now supported. To know these things, open your iPhone Settings>General>About. Version is the FirmWare and Modem Firmware is the baseband.

Before you can unlock your iPhone, you need to jailbreak it first. If you haven’t done it yet, learn how to jailbreak in my previous post (it’s only for 4.3.2) or other posts in the web for other firmware versions.

On the next topic, I will discuss on how to unlock the latest version of iPhone, which is version 4.3.2.