The definition and abbreviation for Potentially Hazardous Food (Time/Temperature Control for Safety Food) or PHF/TCS should be modified to drop the reference to potentially hazardous food and PHF.
Yes, as a treat apples are fine for chickens. Some will say it is best not to feed them too many apples as the seed of an apple has a small amount of arsenic in it.
Apples have minimum calories, maximum vitamins and bioactive nutrients. In 3 days you will lose 5 pounds. You also can try to follow the diet every other day but the result will not be so impressive. An apple diet is very safe and short. Pectin, fruit acids and potassium burn calories, improve your metabolism and digestion. Everybody can do it.