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Un-mapping the domain name from your site will unlink your domain name from your website. This means that your site link of type abc.com/.org/.net ,etc. will change to abc.websites.co.in.
This step is not recommended as it severely decreases your SEO value of the site.
Furthermore, if you unmap your domain, and wish to re-link your domain to a new/same domain, you will not be able to do.