I cannot find the answers for my questions about using Yahoo Mail API for my web site. Please, if you have some information about it - it will be so good!

So, we are ukrainian large web site http://tochka.net/
And we want to use Yahoo API mail (mail server) on our site (for our visitors, about 400 000 active users). And we have few questions about API mail:

1) Does it the same mail in features and design as your main mail (on yahoo.com) ? If no - what is the differences ?
2) Is there advertising ? If yes, is it possible to disable ?
3) Can we create our own design ? (for example - use our dashboard with links to the different parts of our web site on the top of the page)
4) Does Yahoo have the e-mail server in Ukraine ?
5) Can we use our domain ? For example, it will be look like "mylogin@mydomain.com" or "mylogin@yahoo.com" ?

Thak you!