Any Good apps for iphone 4?
you can get Instagram, Twitter and Facebook if you are into social networking. If you love games, Angry Birds is pretty good. You can also get Pandora for music and PhotoSynth for photos. http://www.techradar.com/news/phone-and-communications/mobile-phones/70-best-free-iphone-apps-2013-663484 has a list of some of the best apps.
Yes, but depending on your operating system, some nice apps aren't available for lower operating systems.