How to update Iphone (4th generation)?

People say you can't update Iphone4 higher than 4.1.2. I want to know if I can using Itunes on my computer. If I can't update it, I won't be able to get the latest apps.

You can update just check for how much space you have and for other question just download itunes on you computer and sync your apple account

The iPhone/iPod 2 can only go to iOS 4.2.1. The iPhone/iPod 3 can go to iOS 4.3 (i found out because i bought a third but in the end it was a second) the iPhone/iPod 4 can go to iOS 5.
Don't ask about the iPads.
You can use iTunes on your computer to update. (sorry I uninstalled it so no screenshots)