There are a lot of tasks that need doing to keep a ship running long term that can be ignored if you only need it to work for a few hours - you don't need to worry about routine maintenance or shift changes. You might worry about damage control, but if there is nobody available to do it you just have to hope for the best and try not to get damaged.
It has been clear for a long time in Trek that the minimum crew complement is a lot less than the optimal crew complement. As in, a couple of orders of magnitude less.
From the delta quadrant, presumably EDIT: explicitly by transwarp conduit.
Borg queens were introduced in Star Trek: First Contact (the film), and have been seen in Voyager, and previous seasons of Picard. EDIT: It is not clear to what extent the various borg queens are the same individual - several bodies have been destroyed, but how much continuity of mindstate there is between them is an open question. Except that the one in the previous season of Picard was definitely separate because she was from an alternate timeline (and became decidedly less Borg-like).
They were severely damaged by Janeway in the Voyager finale. How severely was not clear (in or out of universe) until now.
