Yes!!! :D
Japanese iPhone apps work on English iPhones, but if they haven't set it up for English as well as Japanese, all the text will be in Japanese.
yes, but not all iphone 4 apps are available on the iphone 3gs/3g/2g becuase they are too high resolution apps, or need a front facing camera.
Yes, all of them. However, some Iphone apps will not work with the ipod touch, so be sure to check when in the app store.
Well, the iPhone 3g has a camera so any apps that have to do with that won't work. Other than that no.
iPhone Apps, including games, work only on iPhone, iPod Touch and some work on the iPad.
no, iphone apps are only made to work with iphones, not other phones...
Yes most of them are the same apps and will work on one or the other or both.
only games can
Yes. Yes they do. But apps with location services won't be able to find your location.
Many apps will work on the iPhone, iPad and iPod Touch. Some are written just for the iPad while others only work on the iPhone and iPod Touch. Under the title in the App Store it will specify which devices the app will work on.
iPhone apps work on iOS devices (iPhone, iPad or iPod Touch) they will not work on a Mac running Mac OS X 10.7 (Lion) or any other Mac OS X version
No, apps are not only for the iPod Touch. Apps were actually made for the iPhone, but they have made most to work with the iPod Touch, too. Apps are only made for the iPod Touch (all generations) and the iPhone (all generations). Apps are made for Ipads to
The apps from the Apple Store will only work with Apple's iPhone and iPod Touch.