1. Tribal society has chiefs as their leaders. Nations are more complex, because they have multiple levels of government and a bureaucracy.
Once again, because you apparently haven't figured out how this whole reading thing works. Address the fact that you fucked up by bringing up population when by your own admission it's irrelevant, and
be fucking SPECIFIC. What specific, objective characteristics defines a chief as opposed to a lord? What does "more complex" actually mean? How many "multiple levels" of government and bureaucracy are required, and what are each of these multiple levels composed of and what do they actually do?
One more vague non-answer out of you and we're done.
2. You have it wrong. The kings in the medieval times did have absolute power. There was a concept that they had divine right to rule. Kings had the power to disinherit rebellious vassals, order taxation, and make laws for the entire kingdom. King Henry II established Common Law in England.
Bull fucking shit. As I said, they can order taxation (as in, taxation of direct vassal lords, not taxation of said lord's subjects) and set obligations for their vassals. Yes, they can also disinherit rebellious vassals, assuming said vassal loses their rebellion (which is far from guaranteed). As for common law, if I may do what you often do in these situations and quote the Wikipeds.
Since 1189, English law has been a common law, not a civil law system; in other words, no comprehensive codification of the law has taken place and judicial precedents are binding as opposed to persuasive. This may be a legacy of the Norman conquest of England, when a number of legal concepts and institutions from Norman law were introduced to England. In the early centuries of English common law, the justices and judges were responsible for adapting the system of writs to meet everyday needs, applying a mixture of precedent and common sense to build up a body of internally consistent law. An example is the Law Merchant derived from the "Pie-Powder" Courts, named from a corruption of the French pieds-poudrés ("dusty feet") implying ad hoc marketplace courts.
Following Montesquieu's theory of the "separation of powers", only Parliament has the power to legislate; but in the event of a statute being ambiguous, the courts have exclusive power to decide its true meaning, using the principles of statutory interpretation. Since the courts have no authority to legislate, the "legal fiction" is that they "declare" (rather than "create") the common law. The House of Lords took this "declaratory power" a stage further in DPP v Shaw,[50] where, in creating the new crime of "conspiracy to corrupt public morals", Viscount Simonds claimed the court had a "residual power to protect the moral welfare of the state".[51][52] As Parliament became ever more established and influential, Parliamentary legislation gradually overtook judicial law-making such that today's judges are able to innovate only in certain very narrowly defined areas.
https://en.wikipedia.org/wiki/English_common_lawTo sum up, it was basically the wild west of legal systems until parliament came along and took control over the whole thing as part of their gradual chipping away of the nobility's power.