Hidden Quest

If you try to clear it in a short amount of time, you'll inevitably end up watching a lot of ads, which is quite stressful. The ads come so frequently that you can't even play other games while watching them, so it's just about right to play while watching YouTube. Even if you try hard, receiving quest rewards is also quite delayed. It seems like contacting support fixes it, but if you don't have high stress tolerance, you might be better off saving up through other means.