-> Cocoa Touch
Multi-touch events and controls
Accelerometer support
View hierarchy
Localization (i18n)
Camera support
-> Media
OpenAL
Audio mixing and recording
Video playback
Image file formats
Quartz
Core Animation
OpenGL ES
-> Core Services
Networking
Embedded SQLite database
Core Location
Threads
CoreMotion
-> Mac OS X Kernel
TCP/IP
Sockets
Power management
File system
Security
Along with the Xcode tool chain, the SDK contains the iPhone Simulator, a program used to emulate the look and feel of the iPhone on the developer's desktop.
Smart developers get mastery over Objective C, C, C++, etc so they can make iPhone apps of any scale and can customized it at any scale. Moreover, they learn use of Cocos2d and Unity 3D for the game development because both programs help to develop 2d and 3d games in iPhone.
As stated earlier you may have seen the list of the skills you need to use iPhone SDK therefore iPhone developer must be hard worker and create innovative, unique and user-friendly applications developer must need the profound experience of developing various types of applications coming from different industries. Developer should have an eye for details and further should have good communication ability to deal with various kind of the clients coming from around the globe.
Read More:- iPhone App UI Designing—Makes It Decent