Yes, it is. However, reinstalling the OS is not a general maintenance routine. It is a solution to an otherwise unsolvable problem. Which otherwise unsolvable problem are you trying to solve?
The process you're referring to is called an archive and install, preserving users and network settings. Steps to perform it can be found on www.apple.com/support. As MisterMe posted however, its generally a last resort if your computer's core system files are damaged or altered somehow that prevents them from working correctly.
Yes, it is. However, reinstalling the OS is not a general maintenance routine. It is a solution to an otherwise unsolvable problem. Which otherwise unsolvable problem are you trying to solve?
It is my understanding of the rules of this forum that aiding users in violating software licenses is not allowed. Installing MacOS X on a Hackintosh is a violation of the MacOS X EULA. Please take your question elsewhere.