Are all ballet turns (flat ballet slippers--NO POINTE) done on the ball of the foot?

Yes every turn in ballet, unless a choreographer wants to do one on the heel or something, is done on the ball of the foot. However, the dancer may or may not be in a high releve for the turn. For instance in some pas de basque you are on a flat foot in plie, but your weight is on the ball of your foot, and also in promenade you can be on a flat foot with weight on the ball of your foot. So basically every turn you are on the ball of the foot, but you might not always be en releve. In pique turns you roll through your toes to your just on a high releve, you don't keep you toes pointed, and in chaines you are on a high half point the whole time, the toes never pointe completely