Stem Cells. Hope this helps.
DNA or RNA surrounded by a protein coat
A chemical change or it also can be named a chemical reaction
No, although there are several theories with increasing evidence, there is still no way to know for sure how it occurred. The great mystery of the beginning of universe is way too vast and vague. Theories can only be proven by presenting a solid proof, but great creations such as universe itself doesn't have to be solved. Various possibilities must have happened or there must be a one conclusion leading to its existence; but moreover, it is not our problem to solve. The confirmation of beginning of its existence will only feed the curiosity of humans.
