The subdomain for the addon domain should be listed on the Subdomains interface, under the heading Modify a Subdomain. You can change the document root and redirect the subdomain as you can with other subdomains.
There is no functionality that I can find that will do this in a way that wouldn't be difficult. It would be easier to just delete it and re-add it using the new subdomain. Would take a backup prior incase any settings are lost.
What backup, Site backup or Setting backup? If delete then does this delete database and files location?
cPanel backup.
No it doesn't delete site files or database, the emails should stay as well but filters/forwards/autoresponders might get removed.
No it doesn't delete site files or database, the emails should stay as well but filters/forwards/autoresponders might get removed.
Sorry, I am not understanding about cPanel backup and where can do this backup? If doesn't delete site files or database then what does this backup?
I'm not fully understanding why you need to modify the subdomain that's created for an addon domain. The addon domain is directly associated with the subdomain created for it and it's only used internally.