A lot of todo-list apps such as Wunderlist offer some kind of reminder feature which usually just fires off a notification.
But I have never encountered an app that offer a similar notification view as the built in preinstalled alarm clock. You know, that locks the phone and offers a snooze option.
This makes me wonder if the alarm clock functionality that is built into the preinstalled iOs app from Apple including setting time or add a snooze button etc is only available for that particular app?
Since I'm a designer without any coding skills I only want to know if it possible or not.
Unfortunately this is unavailable for developers. You can check all of alarm clock apps in AppStore, all of them are using the standard local notifications. Which will fire once and that's all. You can of course set your custom sound and change couple of options, but it will never work like one build in Clock app inside iPhone.
You can read more about local notifications in Apple documentation: https://developer.apple.com/reference/usernotifications/unnotificationrequest