This command can be used to return to the start point and restart an already completed (or already partially completed) quest. NOTE: Sometimes this command can result in a bug that prevents you being unable to progress in the reset quest again.
resetquest [quest id]
|Quest ID||The ID of the quest you wish to uncomplete and return to the initial stage of.|
The above command will restart the quest Institutionalized (because Institutionalized's ID is 000229ec).