I want to provide Virtual Office solution to my clients, what kind of
telephone system/device i need to achieve the following.
1) Give dedicated telephone number to client so when customer call in
with that number , the screen will pop up the number customer dial and
so the customer service can speak with the associate company name.

Try call one of the companies that do excellent Virtual Office Solutions.

I found City Office - http://www.yourcityoffice.com to be very helpfull.