No Hidden Quests, But...

I thought there were no more hidden quests after clearing Area 10, but other people have them. Is there a limit on the number of people, like a first-come, first-served basis? Do people who achieve it first automatically get it? At least there are time-limited quests, so it's a slow burn. I'll play until the time-limited quests are gone. I wonder if hidden quests will pop up again while I'm playing 😳.