There are 15,000 Applications!
The iPhone has thousands of free applications, including food diary applications. Fatseeker and GoMealsHD are two apps that are free and have received good reviews. There are many more using the search feature on the iPhone as well.
As many as you want. I currently have over 500 on mine.
Almost all of the applications on the iTunes store is compatible with the iPhone 4. Exceptions are applications which are for the iPad.
Yes.
Yes It Does, If You Download To Many Apps Or Run To Many Applications At Once It Might Glitch
Two of the highest seeling iPhone applications include Text Lingo and Angry Birds. See 'related links' below.
No, not all applications are priced. Many useful apps are free.
In total there is twenty applications in one folder.
There are several unauthorized 'hacks' available that will allow the user of an iPhone to install applications that will appear in the main menu; however, these programs are not authorized by Apple, and can void the warranty on the iPhone, or prevent the user from seeking service from Apple. Apple has announced plans to release a SDK (Software Developer's Kit) for the iPhone / iPod touch in February 2008, which will no doubt result in many 'native' iPhone / iPod touch applications shortly thereafter.
This really depends on the memory of the iPhone handset as there are different GB.s storage capacity on different handsets starting from 8Gb
iPhone applications are individual applications that do different things. Developers from across the world design and implement applications to do things like edit pictures, connect with friends, etc. The majority of applications are games, whereas others are utilities. See 'related links' below.
There are the basic 'built in' ones that are pre-installed from the factory the limit of how many depends on the memory of the handset.