Can two different websites using the same domain name reside in two different hosting companies and which one will be seen on the web?

Answer 1

Nope.This is impossible because of the way the domain name system (DNS) works: There are some top level domains (TLDs: .com, .info, .us, .uk, etc). Each of these TLDs has a separate institution which administrates the registration of domains (e.g. Google.com). This domain can only be registered once, until it expires. During the registered period, the registrar holds control over this domain. The registrar then allows their customer (the company, institution or individual requesting the domain) to point to name servers. These servers hold the sub-domain (www., mail., ftp.) records for the domain, as well as the address records for the domain (these can be MX records, A records, CNAME records, AAAA records, etc) itself. Although multiple addresses can be configured to be pointed to by a domain, this is almost exclusively done by sites with HUGE traffic, such as google.com, as a load balancing technique. This is because there is no real further control which address the visitors browser chooses to connect to.