Can i upgrade an old iPhone 3?

I have been given on i phone 3, but when i go into app store it won't let me download facebook, watapp or even ebay? It says this app requires ios 5 update required, how do i upgrade? I think its on ios 4.2 at the min.

Keep in mind iphone 3 has hardware that is 6 years old or so now, so even if you could upgrade it would be slow just because that hardware is so far behind.

First off its called the iPhone 3G.
Secondly, no you can't.iOS 4.2.1 is the last firmware available for it.

New upgrades no longer support the iPhone 3G