Question #08: Red places this tile (not the last one of the game). How many points does each player score, if any?

Answer #08: Red is the only player scoring in this case. The completion of the unoccupied road triggers the scoring of the castle occupied by the
Red Ringmaster.
The completed road is worth 6 points (3 tiles x (1 point per tile + 1 point for the German cathedral) = 3 x 2 points )
The
Red Ringmaster will score 6 points for the road but no points for the ringmaster bonus, since the meeple is not on a feature from the base game. HiG only grants this bonus if the ringmaster is on a road, in a city, on a monastery or in a field. (They may revisit this limitation eventually.)
Bottomline:*
Red will score 6 points for the castle.
Note: If HiG reviews the rules as recommended by the community, the
Red Ringmaster could also score a ringmaster bonus of 4 points:
* 2 points for the acrobat space in the castle fief
* 2 points for the circus space in the castle fief
But this is not official and we don't know yet if it will ever be at this point.