There can be many reasons, and often there will be an error message to tell you what it is.
Some possibilities:
No, you do not. Everything will remain the same when you update your iPod when it comes to apps.
Yes. It's also free to update payed apps, that you already bought.
First you go to your app store. Next click on the tab "updates" under all apps. Then it'll show all your updateable apps. Choose 1 and hit "update", it'll ask you for your password. To update all those apps hit "update all" then type in your password. Hope this helps!
No, but in appstore you can just click update all, and it will do it for you.
On the App Store where you gets your apps from hoped it helped
mmm go to my documents/music/itunes/mobile applications delete the apps directly from that folder to prevent them from syncing back to your device
It means that you need to update either your software or apps depending on what the message is asking you to update.
Yes I believe they are free
If you jailbroke it by using cydia all the apps and cydia apps will get deleted
Open up your Library to the Apps tab then hit Check for Updates.
When you update your iPod 4gen it should not screw up your iPod. You apps will still be there.
you go on the app store then updates then click on the app you want to update then tap the update button