A device model can be deleted from the application.
Device Model Dependencies: When a device is created based on a specific device model within the application, that device model becomes a dependency for the device instance. Consequently, the device model cannot be removed while any device instances based on it still exist. Users must delete all device instances associated with the device model before they can delete the device model itself.
All Device operations require necessary permissions. Refer User Profiles document for more details.
To delete a device model,
Access the Developer Application.
Select Device in the left pane.
Hover over the Device model you want to delete. For this illustration, we will be deleting the device model: Dell Gateway.
Click the ellipsis icon that appears.
Choose Delete from the drop-down list.

Click Check Dependencies in the Model Delete Validation popup.
Click Delete in the Delete Model popup.
The device model will now be removed from the application.
See Also