can someone explain to me why these answers are incorrect? then explain the correct the answer?

Answer:
They are incorrect because they add an extra word to them plus it would not sound right if it said I worked on my homework since of 5 in this case you would take out "of" same with spanish you would not add " hace" into the sentence
desde hace basically is a 2 word you add to when it's past tense
Question 2: Hago la tarea ____ las cinco.
Answer 2: Hago la tarea desde las cinco.
Translation 2: I do the homework since five o'clock.
Question 3: Ellos reciclan ____ las tres.
Answer 3: Ellos reciclan desde las tres.
Translation 3: They recycle since three o'clock.
Question 4: Nosotros bailamos ____ cinco minutos.
Answer 4: Nosotros bailamos desde hace cinco minutos.
Translation 4: We have been dancing for five minutes.
Question 5: Mi madre cocina ____ las diez de la mañana.
Answer 5: Mi madre cocina desde las diez de la mañana.
Translation 5: My mother cooks since ten in the morning.