We'd love to help, but you've got a huge number of questions about things over 2500 years of history. Typically, better discussion occurs when you can narrow your topic. Consider posting another question with a much more specific place and date.

Use a double space to leave...

... a line between your paragraphs, at present this is almost incomprehensible.

I think your entire premiss 'relevance and irrelevance' is flawed. If a nation has had an impact which lasts centuries, if not millennia, then how can they have become irrelevant? They have remained relevant became of the impression they have left, their legacy if you will, which is not something directly related to their current standing as a political or military force in modernity.

Ultimately, I think your approach and understanding of history on a macro-level is too unsophisticated to incorporate into a holistic explanation or enquiry. Judging a polity's 'relevance' based solely on economic or military output at any particular juncture is a crude metric which places far too much emphasis on the teleological outcome rather than understanding these societies in their context and drawing useful comparative aspects for future study or discussion.

I would recommend reading Max Weber's Economy and Society to gain a grounding in how comparative macro-history should be pursued.

(Addition):

Every other forum has pointed out that you need to define what 'relevance' means. You should do so if you expect any productive discussion. At present you shift the onus of defining your term onto others, this is either cynical, at worst, (allowing you to say, "Oh, but that definition isn't what I meant") or, at best, demonstrative of a lazy approach to debate and discussion (ie. not putting in the critical thinking you expect of others).

Sorry, we don't allow throughout history questions. These tend to produce threads which are collections of trivia, not the in-depth discussions about a particular topic we're looking for. If you have a specific question about a historical event or period or person, please feel free to re-compose your question and submit it again.

Despite the question being removed, think carefully about what you mean by 'relevance' and post it on 'Free-for-All Friday' or 'Theory Thursday'.