how to get last revision id created after wp_update_post

You can use wp_get_post_revisions.

<?php
// some logic here

$post_id = wp_update_post(/* ... */);
$latest_revision = array_shift(wp_get_post_revisions($post_id));

if ($latest_revision) {
   // do stuff with the latest revision
   // $latest_revision->ID will contain the latest revision
}