Questions about new website launch?

Hi, I have many queries about my new website: 1) Is it true that I need to buy domain name from all the countries? 2) If I buy a domain name (from vendor say godaddy), is there a chance to steal/buy the same domain name by big companies? 3) Once I get domain name, I have to get web hosting vendor, how to... show more Hi,

I have many queries about my new website:
1) Is it true that I need to buy domain name from all the countries?
2) If I buy a domain name (from vendor say godaddy), is there a chance to steal/buy the same domain name by big companies?
3) Once I get domain name, I have to get web hosting vendor, how to believe this vendor about protecting my html and server pages and also the database behind it? Is there any chance of selling(web hosting vendor) my website content to other big companies if they offer more?
4) How about hosting my website on my desktop by making it online 24/7? If so, what are all the security steps I need to take? And how I can bare millions of hits? How about the scalability?

Thanks a billion!
-Chintu
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