Shift + Click on 'Update' button in iTunes?

[mi986]

I know you can Shift + Click on the 'Restore' button in iTunes to restore with a specific .IPSW, but can you do the same with the 'Update' button?

I want to upgrade an iPhone 3GS on 3.1.3 to 4.0 but I don't want to lose any of the data on it. I have downloaded the 4.0 firmware elsewhere (because my internet is really slow) and want to update using this computer.

Will this work?

 

[codenamecueball]

I know you can Shift + Click on the 'Restore' button in iTunes to restore with a specific .IPSW, but can you do the same with the 'Update' button?

I want to upgrade an iPhone 3GS on 3.1.3 to 4.0 but I don't want to lose any of the data on it. I have downloaded the 4.0 firmware elsewhere (because my internet is really slow) and want to update using this computer.

Will this work?

Sync your 3GS and let it run a full backup and snc then shift+restore

 

[draz]

If the firmware update wipes the phone clean then just restore back and it will all come back to how you had it plus the new firmware installed.