Hello @JINGYU KIM , As far as I know, Azure applications and their associated URIs are not automatically deleted by the system due to inactivity or lack of engagement. However, there are some scenarios where an administrator or an automation script may intentionally or unintentionally delete the application. In such cases, the application registration enters the soft-delete state by default.
You can restore soft-deleted items in the administrative portal or by using Microsoft Graph. Not all object classes can manage soft-delete capabilities in the portal, some are only listed, viewed, hard deleted, or restored using the deletedItems Microsoft Graph API.
I hope this helps! Let me know if you have any other questions.