Is it possible to make alarm clock app for iOS?

I found 3 threads in this forum with same question and no reply...
I want to know is it possible to make an alarm clock application for iOS? The app has to ring at a specific time with a custom audio and play the sound as long as the user won't react - like in built-in clock app. (Not just sending a notification!) Is there any API for such functionality? Or is there any other way to do such application?

P.S.
I make the app with Xamarin iOS using both Visual Studio for Mac and Xcode. But any help will be great!

Is it possible to make alarm clock app for iOS?
 
 
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