duplicate content hurts the seo ranking of that site. When google establishes the dates of which the articles where posted (based on blog dates or last updated dates) the first site will have less impact that the last site.
It wont matter to you unless you have links on these articles that you wish to gain seo benefit from.
I would suggest posting unique content to be fair to the people that are giving you a platform.
Duplicate content is strictly prohibited high authority blog never accept your duplicate content. When you planing to guest post every time post unique quality post If your post did not added any value to reader this content will not helpful for you. Always try to add value in your content.
Some time I use archive.org content but always check plagiarism with out checking plagiarism never publish any content. Best of luck happy guest blogging.
Initially I used to post the same blog in different sites to gain visitors: I have seen my rankings hampering owing to the same:
Hence I have selected high PR sites , posted the best content in it and if i have to use the same in another site, I gave reference to the site which created a positive score in terms of ranking.....Its trial and experience method though
You cannot post the article, you can only submit it to the owner of the website or blog, and they will do the posting after thoroughly checking it. If they find it's not unique, they will reject it. You will most likely, not be able to approach them with another article, even if it's a unique one.