Azure Notification Hubs REST API - Direct Send

Question

We have a question in reference to the documentation of Azure Notification Hubs REST API. Specifically, the Direct Send option.

Documentation:  https://learn.microsoft.com/en-us/rest/api/notificationhubs/direct-send  

We have been using the header, "ServiceBusNotification-Tags" for a few years now to target specific device/user groups,
using the URI https://[client].servicebus.windows.net/[client]/messages?api-version=2015-04

Recently we've wanted to use "ServiceBusNotification-DeviceHandle" to target a specific device and have learned about the "&direct" parameter.

1. We have never used the "&direct" parameter when including the "ServiceBusNotification-Tags" header.   

    Is it necessary for Tags ?  

2. Is it true that the "&direct" parameter must be present in the URI in order to use the "ServiceBusNotification-DeviceHandle" header value ?  

We're, looking for a complete understanding of how and when the "&direct" parameter must be used.