Because freshly washed skin created a barrier for active elements of the serum to get it.
It depends on age and possible other specific. On average: the Full Course create the effect for around 3 years. Not more often than one full course a year.
Until visually signs of autoimmune alopecia disappear and hair starts to grow. One course is often enough to achieve that.
No it can’t. Dibaxidil 700 is not a drug and was not tested on children younger 14 or on pregnant women.
It is absolutely unnecessary. Keep using your regular shampoo/conditioner.