How much iPhone 3G applications?
depends on the app, some are expensive and some arnt
How much memory in the iphone can be used for applications?
Do you need an iPhone to install iPhone applications on your phone?
yes then what would the purpose be but you dont have to get them on your iphones apple store you can get and app on your computers applestore
Are the IPhone Clones able to run all the applications from the real IPhone?
No, because they don't have the iPhone OS. They aren't clones even really, just look-alikes.