Can I still have several email addresses under one account?
If you have an old account you can still choose to enable to work with old domains like mac.com or me.com in the diffrence settings as for example Messages or FaceTime.

If you want to use your old mail addresses in Mail.app, you have to enable them in:


  https://www.icloud.com/#mail/prefs-addresses


New created icloud.com addresses can only be used with that domain, and don't have access any longer to the me.com or mac.com domains.

Hope that helped you!