Migration from one domain to other domain I have build a D8 website on domain www.example.com/abc and now wants to copy this site to www.example.com/xyz 

Hosting is same

What I did is:
1) copied all files from abc to xyz.
2) Exported Database from abc and imported it to xyz.
3) Assigned new Database name, Username and Password to xyz in settings.php.

When I go to www.example.com/xyz Homepage looks perfect but when I go to inner pages it takes me back to domain www.example.com/abc.

How should I update the URLs?
More than likely, you have a redirect base directive in your .htaccess. This is used when serving your Drupal site out of a subfolder of your webhosting provider's webroot. You should check your .htaccess file for the directive RewriteBase /abc and replace with RewriteBase /xyz
If that still doesn't work, check the vhost entry of your webserver for the same directive.  
Otherwise, if the site still redirects to "/abc", then you may have a $base_url defined in settings.php causing the redirect.