Here's how a real life company would handle the problem:
"This feature has not be implemented"
Or the game would bug out or simply block the user from completing the activity.
Quite stupid to spend so much time an effort for so many unique quests that only 1 person can complete. Sure, for a game with a small user base that could work (still stupid tho), but if the company wants to scale, you gotta reuse already created assets. Because once your user base gets so big, you literally run out of quests because people will complete them faster than you can create new ones.