no software update option iphone 3gs

The option to update without the computer (Over the air) was made available with iOS 5. If your iDevice is using a version of iOS lower than 5, you will need to use iTunes on your syncing computer to perform the upgrade. Use the Apple link below as a guide for the upgrade.

http://support.apple.com/kb/HT4972

Also read the instructions from the section entitled "Update your device using iTunes" at the link below.

http://support.apple.com/kb/HT4623

Information regarding transferring purchases from your iDevice to iTunes on your syncing computer can be found at the link below.

http://support.apple.com/kb/ht1848

Go back to the article you asked this question from, ignore the instructions for updating it wirelessly, scroll down, and follow those for updating it from iTunes on a computer.

(83308)

iTunes running, connect your phone, on the Summary Pane, hit the "Check for Updates" button & follow the instructions.

BACKUP YOUR PHONE BEFORE YOU BEGIN!

You appear to be using an iPhone 3G and not a 3GS; those can't be updated past 4.2.1 and will therefore never have the Software Update option in Settings.

(83311)

You have an iPhone 3G, not a 3GS. There are no further updates for your phone.

You're at the end of the line.

Because many/most app developers no longer support the iPhone 3G.

Look here for apps that will run on your phone:

http://appshopper.com/search/?search=iPhone+3G