How do I change the email address for my apple ID?
Do you need a separate apple ID for a iPhone and different one for another device such as iPad?
iPhone 4S
Do you need a separate apple ID for a iPhone and different one for another device such as iPad?
iPhone 4S
No you don't need a separate one, and you are best with only one Apple ID.
To change the email address see this document:
How do I change the email address for my apple ID?