Yes there is. (See Related Links)
pretty sure all apple ipod touches come with the app store the 4G is coming with a camera
No, you can get it for an iPod touch for the same price. Every app in the app store can be bought for iPhones and iPod touches, but some work best on iPhones, because they need microphones. (you can get these for iPod touches)
iMessage for ios5 or text me which you can buy in the app store
yes if you have the app and internet
Rock band is not pre-installed on all iPod Touches, but every iPod Touch has the capability of using that app.
The built-in Music app views and plays music placed on your iPod Touch by iTunes. On unmodified iPod Touches, the Music app icon is orange and has a note symbol.
Yes but if you delete the app and then download it again you will have to pay again
No but it is avalible on the app store for ipod touches and iphones
Fack no
The iPhone's and iPod touches have ooVoo. You can download it free in the APP Store.
There is now an official Twitter app.
If you are the only one with two iPod Touches, then there's not much to do since it is hard to operate two at once. If it is you and your buddy, then you can download an app from the App Store that allows two iPod Touches to play with each other at once. One example of such an app is Whiteboard Collaborative, a free app that allows you to draw whatever you want with each other in real time over a Wi-Fi network.