Paste the lines below into your wp-config.php file, just above the line /* That’s all, stop editing! Happy blogging. */, to either prevent theme and plugin files from being edited in your WordPress dashboard or to set the default theme for your website. Be sure to replace ‘your-theme-folder-name’ before saving the changes.
Disallow Editing in Dashboard
define( ‘DISALLOW_FILE_EDIT’, true );
Define a Default Theme
define( ‘WP_DEFAULT_THEME’, ‘your-theme-folder-name’ );