Q: I can't download any games to my iPod touch it says I need the iOS update 4.3 version what do I do???

Append the last three characters of its serial number to http://everymac.com/ultimate-mac-lookup/?search_keywords= and load the page; you can then find out what its maximum iOS version is, and can update from iTunes on a computer.

(87604)

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. Note nly the 3G and later can go to iOS 4.3 or later

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

If you have a 1st or 2nd generation iPod, you can use a tool to find compatible apps. Here's my favorite:

iOSSearch - search the iTunes store for compatible apps.

And here are some other people's suggestions:

Vintapps 3.1.3 - paid app.

Apple Club - filter apps by iOS version.