When I migrate to the new panel will I still be able to use my old .comxa.com domain name I was given.
I have lots of link to picture on my old site and don’t want to have to change them all.
Yes you can absolutely 
I have backed up all my files and when I try to move account details a get a message saying “You already have an account in the new panel!”.
If I click on any of the links which take you to the new panel, it just shows the old one.
Delete the site from your control panel, then click your name on the accounts list, delete your profile, you’ll be asked to login again - do this and add your site back to the new panel.