I have planned not to renew one of the main domain on my server. I have other addon domain on this main domain that I want to use as main domain. Is it possible to change the main domain to one of the addons, or do I need to delete everything and start over again?
That is possible but a tricky one. 2 DNS zones cannot exists for one domain. You will need to remove the addon domain first. Make sure to take a backup for the data. Later, replace the main domain name to addon domain.
I am sure there are better ways to do this. If I recollect some, I'll post.
I am not even sure this is possible without something larger than a massive headache. Wouldnt a restore from the backup just backup to the wrong place and throw an error?