Syam Kumar R

Check https://www.webmasterview.com/2009/12/wordpress-feed-sub-domain/ to see how to move your WordPress feeds to a subdomain.

If you don’t want to append an extension (.html) to %postname%, the only (almost) clean workaround is to just append a hyphen.

/%category%/%postname%-/

I tried this with WordPress 2.7 and Top Level Categories plugin and it works.