IOS – Downgrading an iOS application – how to download a previous version

(I'm not certain of this answer -- it's a somewhat educated hunch, based on using iPods for 10 years and Apple products for 25, and looking at wikipedia. If anyone knows from actual experience, use that answer instead.)

In general, I would guess that you can downgrade an iPod to the version of the OS that it was released with, but not earlier. So, for example, an iPod Touch 2g could probably be downgraded to iPhone OS 2.1, but not 1.1 (which wouldn't really matter since there was no App Store in 1.x!). Each iPod Touch gen-N ships with the N.1 release of iOS, about a month after the corresponding iPhone ships with the N.0 release.

An iPod Touch 2g should run all versions of iOS for the iPod Touch that have an App Store, though it doesn't support all the features of iOS 4. The hardware differences between iPod models might be a bigger issue for testing, e.g., older iPods don't have a built-in microphone.

Your question can be rewritten in short form:

1. iTunes: How to move your music to a new computer
2. Where are my iOS backups stored? - expand the section About Syncing and Backups and you'll see

iTunes places the backup files in the following places:

• Mac: ~/Library/Application Support/MobileSync/Backup/
• Windows XP: \Documents and Settings(username)\Application Data\Apple Computer\MobileSync\Backup\
• Windows Vista and Windows 7: \Users(username)\AppData\Roaming\Apple Computer\MobileSync\Backup\

I linked to the official articles since things do change and cutting and pasting the steps today might not be right if things change in a month or two. Don't worry - the article about music moves everything except the iOS device backups. If your device is working, there's no need to move backups unless you want to keep older ones or save time the first time you sync with the new iTunes.