Newbie Question

[natove]

Hi
Sorry for the newbie question but appreciate for answers:

1. Is it possible to add a "Diamond dial" to any Rolex watch model? or does only specific models have the diamond dial?

2. Does all Rolex watches have "His and Hers"? or only specific models?

3. What is the proper term for the "His and Hers" kinds of watches? if any

4. Is it cheaper to buy a His and hers or is it the same as adding the price for male and price for female?

Thanks in advance for you answers