Appointments+ show additional fields and validate field entry

I am missing some functions in 2012-childtheme/functions.php that I wrote for Appointments+ 1.5.6 .. I have now upgraded the plugin to 1.9.2 and need it to

1. show the list of MY Additional Fields in the A+/settings/general/display ... right now it shows nothing
2. validate the entry of one field AND see if the entry is already there and active

here is the old code for validation and check if appointment already has been done

add_action( 'app-additional_fields-validate', 'app_validate_custom_field' );
function app_validate_custom_field() {
	//example field key is firstname
	global $wpdb;
	$field_key = 'id13';
	if ( isset( $_POST[ $field_key ] ) ) {
		$value = $_POST[ $field_key ];
		//^ assert position at start of the string
		//\d only digits used
		//Quantifier: {13} Exactly 13 times
		//$ assert position at end of the string
		if ( ! preg_match( '/^\d{13}$/', $value ) ) {
			wp_send_json( array(
				'error' => '13 DIGITS PLEASE'
			) );
		}
		$IDs = $wpdb->get_col( "SELECT ID FROM {$wpdb->prefix}app_appointments WHERE month('start') = MONTH( NOW()) ORDER by ID ASC " ) ;
		if (  $IDs ):
			$appointments_data =  get_option('appointments_data') ;
			//$IDs[0]  =  660;
			for ( $i = $IDs[0];  $i <= $IDs[count($IDs) - 1] ; $i++  ):
				if (array_key_exists( $i , $appointments_data)):
					if ( $value == $appointments_data[$i]['id13'] ){
						die(json_encode(array(
							"error" => __( 'YOU HAVE AN APPOINTMENT' , 'appointments'),
						)));
					}
				endif;
			endfor;
		endif;
		}
}