In the following example you can see how to disable loading of google fonts on your website with a simple filter.

Best solution is to add custom actions and filters in Child Theme functions.php file. But also you can create your own plugin and use this codes in your plugin.

For disabling comments form on individual single post, First edit your post in backend and like bellow shot, enable Discussion panel and then uncheck Allow Comment checkbox and update post.

• Disable comments on all posts – If you want to disable comments form on all single posts, then go to Dashboard > Settings > Discussion and disable comments and change comments settings.