Flags: get Action after a user flagged a specific number of nodes?
You can able to detect limit has reached using hook_flag_flag hook exposed by flag module..

Flag Limiter module uses the same logic to detect the limit as you can see the below code

function flag_limiter_flag_flag($flag, $entity_id, $account, $flagging) {
  // Get the flag limits.
  $flag_limit = variable_get('flag_limiter_' . $flag-&gt;name . '_value', 0);
  $peritem_limit = variable_get('flag_limiter_' . $flag-&gt;name . '_peritem_value', 0);

  if ($flag_limit) {
    $user_flags = flag_limiter_get_user_flags($account-&gt;uid, $flag-&gt;fid);
    if (count($user_flags) &gt; $flag_limit) {
      $unflag = flag('unflag', $flag-&gt;name, $entity_id, $account, TRUE);
      if ($unflag) {
        drupal_set_message(t("You've already signed up @num times", array('@num' =&gt; $flag_limit)), 'error');
      } else {
        drupal_set_message(t('Fail limiter operation'), 'status', FALSE);
      }
    }
  }

  if ($peritem_limit) {
    $flagging_data = flag_get_counts($flag-&gt;entity_type, $entity_id, TRUE);
    if ($flagging_data[$flagging-&gt;flag_name] &gt; $peritem_limit) {
      $unflag_item = flag('unflag', $flag-&gt;name, $entity_id, $account, TRUE);
      if ($unflag_item) {
        drupal_set_message(t("The event already signed up @num times", array('@num' =&gt; $peritem_limit)), 'error');
      } else {
        drupal_set_message(t('Fail limiter operation'), 'status', FALSE);
      }
    }
  }
}


You can implement same hook in your custom module to redirect user to the page you want.. You can use drupal_goto function to redirect user..

function YOURMODULENAME_flag_flag($flag, $entity_id, $account, $flagging) {
  if ($flag_limit) {
    $user_flags = flag_limiter_get_user_flags($account-&gt;uid, $flag-&gt;fid);
    if (count($user_flags) &gt;= $flag_limit) {
      drupal_goto('path');
    }
  }
}


writing custom module instructions ..


Create a folder called "custom" inside sites/all/modules
Create a folder called "myflaglimit" inside sites/all/modules/custom/
Create a file called "myflaglimit.info" inside "myflaglimit" folder create above.
Put in below code and save file


Below code goes into myflaglimit.info file..

name = My Flag Limit
description = Provides a redirect on reaching limit.
core = 7.x
package = Custom
dependencies[] = flag_limiter


Your logic goes into .module file


Create a file called myflaglimit.module file inside myflaglimit folder you have create with below code
You extend drupal function using hooks which are nothing but functions which starts with modulename_hook


use below code inside module file

&lt;?php
function myflaglimit_flag_flag($flag, $entity_id, $account, $flagging) {
  if ($flag_limit) {
    $user_flags = flag_limiter_get_user_flags($account-&gt;uid, $flag-&gt;fid);
    if (count($user_flags) &gt;= $flag_limit) {
      drupal_goto('path');
    }
  }
}