Regarding question 2) I see the preferred method is:
<?php
if (ValidatedField('ratesandavailabilityx_878', 'ratesandavailabilityx_878')) {
if ((strpos(("," . ValidatedField("ratesandavailabilityx_878", "ratesandavailabilityx_878") . ","), "," . "" . ",") !== false || "" == "")) {
if (!(false)) {
?>