The application must not be registered.
Delete an application
The procedure to delete CF and self-hosted application is similar.
To delete an application, proceed with the following steps:
Click on the "Apps" icon. In the "My Applications" window, select the application that you want to delete and click "Delete".
Only unregistered applications are eligible for deletion.
In the confirmation dialog, click "Continue".
For CF hosted applications, If the app is deployed and not registered ("Deployed" state with warning symbol), then you can undeploy and delete the app simultaneously. To do this, select "Yes" in the confirmation dialog and click "Continue".
The application is deleted.