Can't download facebook in my new iPhone 3GS I bought a new IPhone 3GS and can't download Messenger, Facebook, hike etc.
Why?

How to download?
You can download the last compatible version of an app if you already have the app in your purchase history. You can add the app to your purchase history using iTunes on your computer, since iTunes is version-agnostic.

Once you've downloaded the app on iTunes, it will be in your purchase history and attempting to download it again on your device should prompt you to accept an older version of the app.