upgrade iphone 4 version 4.0 with firmware 1.59.00 to iOS 5 and preserve jailbreak?
If you upgrade your iPhone 4, two possibilities may happen ;
1. If you have a jail broken iPhone, You will lose your jailbreak
2. If you have an unlocked iPhone, you may lost it too.
Before updating your iPhone , you need to take backup of your data files from your iPhone . After that, use Remote unlocking method and (get unlocking instructions from any of the online vendors )to unlock it . It doesn't requires jailbreaking and it is one of the permanent unlocking solution too. After unlocking your iPhone using this method, you can update or downgrade your iphone without any interruption . it won't gets locked again . If you have completed unlocking and updating process, you can use restore service to restore your data files from backup .
Use the following steps to upgrade your iPhone 4 :
1. All normal iPhones (non jailbroken) should choose this method.
2. Check that your device is compatible. iOS 7 is compatible with the iPhone 4 and newer, iPad 2 and newer, iPod Touch 5th Generation. The iPhone 3GS, original iPads, and older iPod touches will not be able to upgrade.
3. Back up your iPhone. Before iOS 7 is released, ensure that you have a recent backup stored to either your computer or to iCloud. This will ensure that you have something to fall back on if the update process doesn't go smoothly.
4
Start the update process. You should receive a notification that the update is available to download. If you do not, open your Settings and click the General option. Select Software Update.
4.If iOS 7 is available for your device, then you will see an icon in the Software Update section. Click the Download and Install button.
5. You will only be able to download iOS 7 on your device if you are connected to a wireless network. If you want to download it on your computer instead, use the next section.
Source : MobileUnlockGuide.com