Do you still have to restart the computer everytime you want to use Unity ? I mean back in the days you had to choose this windows / unity copy and boot that one up.
Yes, but as long as you are in UnityHacksOS you don't have to restart the PC every time, you can Uninjected and Inject at any time without restarting the PC. For more information, you can look here, where it is explained in more detail and shown how to install the hack. https://www.unityhacks.com/threads/installation-guide.17857/