aliases and multiple zoho accounts for free personal email + advice

aliases and multiple zoho accounts for free personal email + advice

I have just opened a free personal email account with ZOHO. I need to know the following:
 
1) can I create one or more aliases (as explained below) or I need to get a domain? I would prefer doing without a domain at this time.
What I want to do is the following, but I can't find the way of doing it:
my account is xxyy@zoho.com. I want to create another email address, for example xx_yy123@zoho.com, so that emails addressed to xx_yy123 will go in the ONE ZOHO' mail box I just opened. At the same time I need to be able to send emails using the xx_yy123 in the FROM of the emai.
 
If the answer is YES (ie, you can have multiple aliases associated with my ONE zoho's mail box), could you please detail how to do it since I can't find the way of doing it.
 
2) how many free personal email accounts can I open?
 
3) I have multiple emails accounts that serve for different things. My YAHOO account and my GMAIL account are very active and have a significant amount of emails stored. They are also connected with my Blackberry Torch with no problems.  
I want to move out of BOTH accounts and eventually close both of them, which is why I opened with ZOHO. I want to move out of YAHOO by the end of the month.
 
I have to transfer the yahoo's email content into ZOHO free personal email. I have LOT to transfer. Do you have a protocol that I can follow to transfer the content of the yahoo mail box into my new ZOHO's mail box?
 
Can I realistically and technically do the above SIGNIFICANT transfer with a free personal zoho's account?
 
Should I get a domain? Would it be better having a domain?
 
At a later time I will have the same questions also for the GOOGLE account. 
 
Thank you. Please answer soon.