Question

I want to send my Application to background simply clicking on Button inside my Application.
Is there any way to call applicationdidenterbackground manually or any other way ?

Answer 1

iOS Human Interface Guidelines says "Don’t Quit Programmatically", whereby quitting must be understood as including "suspending":

Never quit an iOS application programmatically because people tend to interpret this as a crash. However, if external circumstances prevent your application from functioning as intended, you need to tell your users about the situation and explain what they can do about it. Depending on how severe the application malfunction is, you have two choices.

Display an attractive screen that describes the problem and suggests a correction. A screen provides feedback that reassures users that there’s nothing wrong with your application. It puts users in control, letting them decide whether they want to take corrective action and continue using your application or press the Home button and open a different application

If only some of your application’s features are not working, display either a screen or an alert when people activate the feature. Display the alert only when people try to access the feature that isn’t functioning.

If you really want to exit your app programmatically, then you can call exit(0);, but I doubt that you app will pass the Apple review.