redsn0w
It depends on what ipod gen. you have. For ipod touch generation 1, 2, and 3, you can't put a background unless you jailbreak your device and get the right app from Cydia. For ipod touch generation 4, select the picture you want and set for your homescreen or wallpaper. As far as I know you don't need to jailbreak Itouch 4 to set a background. :P
Yes. On your iPod 4g, go on Safari and search for Jailbreak sites.
i don't know someone tell me please
No. the Ipod Touch 4 gen. is the only iPod touch w/ a camera. But the iPod Nano 4 and 5 gen. also have one (note: not all iPod nano 4 gen. have a camera.) Im not so sure the iPod Nano 6 gen. has one, tho.
Only the iPod Touch Gen 4 comes with a camera
No, you can use iMessage on a 3rd and 4th gen iPod Touch running iOS 5.
Yes
Only the Ipod Touch 4th gen. canuse iOS4
This only works on iPod touch third generation, iPad,or iPhone and you have to have iOS 4. If you are using the second generation, you will have to jailbreak you iPod touch.
Search in the internet yourself, there are many ways
2cd generation 64gb ipod touch for 400 dollars
iOS 7 isn't available on 4th gen iPod Touch