Q.Why is it necessary for a country to have clear demarcation of powers/responsibilities in the constitution? What would happen without it?

Even after a group agrees it needs some basic rules to live by, a more fundamental question remains completely unanswered: who actually gets to decide what those rules will say? Different people will honestly believe different rules are best, so before any group can settle on the content of its rules, it first has to settle who has the authority to make that decision at all. Different societies have answered this question in very different ways historically — a monarch alone deciding, a single political party alone deciding (as in the erstwhile Soviet Union), or, in democratic systems, the people deciding, whether directly (as in some ancient Greek city-states, where citizens voted on each matter themselves) or, far more commonly today, through elected representatives. Even choosing representative democracy leaves real questions open — how should those representatives be elected, and how many should there be? A constitution's job is to give a concrete, working answer to all of this: …