What method is not approved for thawing foods?

There are three ways to safely thaw food. you could put it in the refrigerator overnight put it under cool running water or put it in the microwave before cooking.

Well, a method I know that would not be approved for thawing foods are that when the food is completely thawed you can't put it back up to the freezer as this will increase the chance of food poisoning, therefore if it's already thawed it must be cooked immediately to kill the germs.