How long does it take for a human to acclimate?

2 hours

Starting now (mid-2009), something like 15 years before the first launch. Starting from the moment of launch, something like seven months before arriving at Mars.

boys stop growing to the age of 18 and girls grow at 13

up to nine months...somtimes it may be pre mature wich mean the baby is born before due date..

Many years. Probably the whole journey would be so difficult to arrange that it will never be done.