Q: Ask other users about this article

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.

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To update

The Settings>General>Software Update comes with iOS 5 and later.

Connect the iPod to your computer and update via iTunes as far as your iPod model allows

iOS: How to update your iPhone, iPad, or iPod touch

A 1G iPod can go to iOS 2.2 via iTunes and iOS 3.1.3 via

Purchasing iOS 3.1 Software Update for iPod touch (1st generation)       

https://buy.itunes.apple.com/WebObjects/MZFinance.woa/wa/touchLegacyLandingPage

A 2G to 4.2.1. Requires iTunes version 10.X. If a Mac it requires OSX 10.5.8 or later. With OSX 10.4.11 you can only go to iTunes 9.X which gets you as high as iOS 4.1

A 3G to 5.1.1  Requires iTunes version 10.5 or later

A 4G to 6  Requires iTunes version 10.7 or later. For a Mac, that requires a Mac with OSX 10.6.8 or later

Identifying iPod models

Yur iPod may not support a higher iOS

Also

Many developers when they updated their apps to support iOS 5 and 6 dropped compatibility for iOS 4.2.1 and earlier.

Your only way is if you have the version that was compatible on your computer such as in the recycle bin/trash or in a computer file backup. In that case delete the current version that is in your iTunes App library and replace it with the older version. Then sync.

Also see:

I assume you have iOS 4. Perform a update with iTunes.