The most important thing you are adding with nutrient is nitrogen. And the timing of the additions are when the yeast needs it the most. Without proper nitrogen support, the ferment can be sluggish, become stuck, or you get lots of H2S production.
If you want a truly natural source try fermaid O. It is an organic yeast nutrient derived from dead yeast. On the other hand, their is also fermaid K which contains natural organic nitrogen like fermaid O has but also has some DAP and vitamins added. Both sources are great if used correctly with the proper considerations.
Yes that is what he means. Being from Saudi Arabia, what kind of wines are you making? It was always my understanding alcohol was illegal in Saudi Arabia but please correct me if I'm wrong.