I want to know How to promote the single .com website for all countries in world? What are the content and on page technique for this and most important which Geographic target to select under Google webmaster tool.
You probably are aiming pretty high to try and get every country. Many parts of asia and the middle east will be extremely hard for you to rank for. However your best bet/easiest method is to build a solid social media marketing plan for your content to make it go viral. Make sure your content can be read in all the target countries you are aiming for (remember english is only the language of 66% of internet users, and that number is dropping as internet is becoming easier to access).
Then from there if it was me; every new blog post you do/page you add/etc, just keep focusing on ranking for locally for that specific page. It's going to be alot of trial and error, comparing your site to local competitor's in that region, etc.
I think in this occurence, going after big inbound links like wikipedia would also be pretty beneficial.
You dont necessarily need to create a wikipedia page; but you can apply to become an editor and if approved you can help build articles and tie your website in as a resource to support your edits (if your website is a supporting resource).