You do not get iOS 4.0.2 when you update an iPod to iOS 4.1. iOS 4.0.2 is an earlier version and precedes iOS 4.1. The next version after iOS 4.1 will be iOS 4.2.
If you have Terraria on Steam it updates itself once an update is available.
Junk jack
You can't.
The apple iOS 5 update IS OUT NOW
The apple iOS 5 update IS OUT NOW
If you are running iOS 5, you can update to iOS 6.1.3 (or 6.1.4 on iPhone 5) by going into Setting>General>Software Update. If you are running iOS 3 or 4, you can update to the latest software by plugging your iDevice into your iTunes-authorized computer and wait for your device to be recognized. Once this is done, there should be a pop-up to download and update to the new iOS. Everything should be self explanatory by then.
You can update it to iOS 5 the same way you update it to any other iOS version. The 4th generation (and indeed the 3rd generation) iPod Touch can be updated to iOS 5.
iOS 6.0 is expected in October of 2012.
The iOS 4.3.5 update was a security fix.
The 8gb iPod is not capable of downloading the IOS 4.3 update. If you want to run IOS 4.3 on your iPod, you will need to update to at least a 32gb iPod.
Dont update to iOS 6. It runs bad on the ipod touch and when you jailbreak it, it will be only slower. I will downgrade to iOS 5.1.1 since it is the best for me right now.