This code recipe allows you to restrict members in specific countries from signing up. The restricted countries are defined in a $restricted_countries array of level IDs and country codes (see the $pmpro_currencies array in the plugin file /includes/countries.php for included country codes)….
Use this recipe to mark one or more membership levels as a one time trial. New members will be able to complete registration for the one time trial level. If they attempt to renew the trial level, a message will be shown that their one time trial has already been used. We recommend this method for sites looking to add a “no credit card required” trial option.
Note that this method will only keep the same user from abusing your trial level and completing multiple checkouts. People can still reuse a trial if they sign up with a new email address and create another user account on your site.