A Unity ID allows you to buy and/or subscribe to Unity products and services, shop in the Asset Store and participate in the Unity community.
Separate names with a comma.
There are two buttons on top of the HoloLens band on each side. One side adjusts brightness and the other adjusts audio volume.
Did you install using the UnityDownloadAssistant.exe? That should let you install the UWP components, while I assume using just the editor...