Hi Raman--
Sorry to answer your questions backwards. With that said my reply to question 2 would be that each of us is able to make whatever positive changes needed to continue our growth and learning while we are here. Of course keep in mind some people are not as "awake" as others and see no need to change or grow. I have found many times in life that the saying of "What goes around comes around" holds true inmany ways. If you send out bad it comes back bad and same for good. If your intention is to attempt to help somebody get in touch with the positive side of their number maybe you could point out and reinforce some of the positive traits they have and try to ignor or feed into their negative traits.
As to question one... this is a bit more complicated. While many people share the same life path number there are other factors that are completely unique to each person. For example the life path number may be the same, but their astro chart will be different, along with their names adding up differently, and so forth. So to try and say it easier, you'd have to provide much more info about the people involved, and then compare the many different factors that make up each person.
As to the sun and moon part of the question - many people believe the moon has a great influence on us, as well as the sun. So in part that could make a difference, but it is only a small piece of the puzzle. You have to look at the entire picture not just random pieces of it.
Numbers are only one part of us. There is also the planetary lineup at birth, our names, our enviroment, etc.
Not sure if I answered what you needed but hopefully I gave you more to think about!!
