Eating one meal a day resembles the intermittent fasting that most people nowadays tend to engage into. Hence, one benefit of doing this on a regular basis would be weight loss. Other than this, I cannot think of anything else that would prove that this eating habit is advantageous.
Now going to the "don'ts", I think this is not entirely different to a person experiencing hunger. Remember that when you eat once a day, assuming you are going to eat for just an hour, then you will spend the rest of the day drinking only fluids. I don't think a person can eat a single meal that can suffice for the calorie requirement per day, especially when you have an active lifestyle. Hence, as a hungry person, eating once a day may make you feel irritated, grumpy, and will make you lose your focus and concentration.