how can we rename the wp-includes folder.We don't want folder name wp-includes displayed in source code
The name of
wp-includes folder is hardcoded in multiple places on WordPress core, as well as
WPINC constant which isn't conditional and can't be changed.
Renaming it would take creating and maintaining a fork of WordPress core, which is impractical.
Your best bet is just keeping it out of front end, for example by redefining any assets loaded from it to different URLs.