Question about Outlook Express

Hi I have configured Microsoft Admin Center to be my Company's Mail exchange domain but am facing some few challenges.

1.  I would like to know how I can Edit the details of the members accounts from the admin center administration panel, i.e the Name, the password, the e-mail address associated with the account.
2. I would like to know how i can configure the log in part such that the members do not have to put the whole e-mail address as the username i.e to eliminate the @mydomain.com post-fix of the e-mail address.
3. How do I create e-mail alias of a custom domain e-mail account for a custom domain account i.e an alias *** Email address is removed for privacy *** for *** Email address is removed for privacy ***

I would highly appreciate if I can get assistance for the above challenges.

Thanks