Duplicate comments

I was working on the function of duplicate comments. I have the fallow code in the comment.php file of wp-inlcude but its not working:

**
 * Validates whether this comment is allowed to be made.
 *
 * @since 2.0.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param array $commentdata Contains information on the comment
 * @return mixed Signifies the approval status (0|1|'spam')
 */
function wp_allow_comment( $commentdata ) {
	global $wpdb;

if(is_page(2999)){

} else {

	// Simple duplicate check
	// expected_slashed ($comment_post_ID, $comment_author, $comment_author_email, $comment_content)
	$dupe = $wpdb->prepare(
		"SELECT comment_ID FROM $wpdb->comments WHERE comment_post_ID = %d AND comment_parent = %s AND comment_approved != 'trash' AND ( comment_author = %s ",
		wp_unslash( $commentdata['comment_post_ID'] ),
		wp_unslash( $commentdata['comment_parent'] ),
		wp_unslash( $commentdata['comment_author'] )
	);
	if ( $commentdata['comment_author_email'] ) {
		$dupe .= $wpdb->prepare(
			"OR comment_author_email = %s ",
			wp_unslash( $commentdata['comment_author_email'] )
		);
	}
	$dupe .= $wpdb->prepare(
		") AND comment_content = %s LIMIT 1",
		wp_unslash( $commentdata['comment_content'] )
	);
	if ( $wpdb->get_var( $dupe ) ) {
		/**
		 * Fires immediately after a duplicate comment is detected.
		 *
		 * @since 3.0.0
		 *
		 * @param array $commentdata Comment data.
		 */
		do_action( 'comment_duplicate_trigger', $commentdata );
		if ( defined( 'DOING_AJAX' ) ) {
			die( __('Duplicate comment detected; it looks as though you’ve already said that!') );
		}
		wp_die( __( 'Duplicate comment detected; it looks as though you’ve already said that!' ), 409 );
	}
}

If its page id 2999 then duplicate is allowd else not.

Even if i change the if statement to the fallow it doesn’t work

/**
 * Validates whether this comment is allowed to be made.
 *
 * @since 2.0.0
 *
 * @global wpdb $wpdb WordPress database abstraction object.
 *
 * @param array $commentdata Contains information on the comment
 * @return mixed Signifies the approval status (0|1|'spam')
 */

function wp_allow_comment( $commentdata ) {
	global $wpdb;

$string = "home";
          $container = $post->post_title;
            if(strstr($container,$string)) {

} else {