Question: Is it possible to search those site who are not submitted/registered on any search engine in world? 

Answer: Search engines follow all links on a website. If the site has links to it from another website, it will eventually be found and show up in a search.\nIf it has no links from another site and is not submitted to a search engine for crawling it will not be found. (Although there is a theory that some search engines crawl all registered domain names- This is not proven.)
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