Yahoo mess chat...............?

Hi

I have two questions. The one who answers both clearly can gain 10 pts.

First quest:-

while chattting in a chat room with a nickname & giving an IM our nickname appears in the messages list. Isn't??

But the members in that chat room are able to find my original yahoo id. (even by knowing the nickname)
How is that ? Please xplain the procedure for knowing that.

Second Quest:-
I'm Having Y! mes. 7.5 with Voice. In any chat room or in any conferences the "Voice" button is visible. But when i IM my friend (in my buddy list) (only one friend) that voice button is not available.

Is it not possible to have a voice chat with any one friend separately???? (one-to-one ; not in a conference)
Please xplain me with procedures.

Thank you.

Self explanatory. the answer is all there in the messenger.
(I hope you find it right after you received my reply from your personal E-mail)