I have an iphone 3g ios 4.2.1 not jailbroken. I want to download apps, games and ebooks but?

When I install any application or game its says NEED NEWER IOS VERSION. I know that iphone 3g is upgrade till ios 4.2.1, that I have. I don't understand what is the use of iphone 3g when a single app or game is not downloading. When I used iTunes in downloading apps or games it download perfectly but can't drag and install in my iphone 3g, it says same as I said above. I want to know why its happening and is jailbreaking iphone last solution of downloading apps and games? And can I download apps and games without jailbreaking.

Yes. Many of the apps in App store have a minimum requirement of IOS 5, And your iphone is struck at IOS 4.2.1, Apple has not updated iphone 3g because its very old and its Hardware can't support newer operating systems. There would be no use even if you jailbreak because it will slow down your phone and it would be terrible to use. The only solution you have is to Buy a new phone…

For 4.2… Hope this helps. I stumbled on this playing around with my old 3GS.
Best luck.