Change email of Apple ID

See the rules for changing your Apple ID https://support.apple.com/en-us/HT202667 Once you have decided for sure what you want to do and if doing so is "legal" see:

Before changing your Apple ID using a computer, sign out of all Apple  services that use your Apple ID. If you are going to use an iPhone, iPad, or iPod, then stay signed in with your Apple ID on only that device. This instruction is taken from the above documentunder the heading Before you change your Apple ID.

For sign out purposes, see Where can I use my Apple ID? https://support.apple.com/en-us/HT202659 “This list is provided for informational purposes only and is subject to change without notice. It's not intended to include every feature or service that uses Apple ID. Visit the Apple ID support page for more information.”

There may be some redundancy, but see What to do after you change your Apple ID or password 

 https://support.apple.com/en-us/HT204071

You can't remove/change @iCloud.com, @me.com or @mac.com aliases.

iCloud - Create or change email aliases.   

If you create a new iCloud alias, you can't use a new alias as your Apple ID. You can only use aliases that have a question mark on the right side. Log into your Apple ID to check.

Apple ID - Manage