Why do I get errors abot undefined variables and errors with unserialize()?
The best way to get the issue resolved would be to file an issue for the Commerce Kickstart project on drupal.org.

The reason you're receiving those notices is because ideally, in a perfect world, line 1305 would say something like this (to avoid such notices):

  if (function_exists('i18n_string_update') &amp;&amp; isset($instance['widget']) &amp;&amp; isset($instance['widget']['type']) &amp;&amp; $instance['widget']['type'] == 'link_field' &amp;&amp; isset($prior_instance['settings']) &amp;&amp; isset($prior_instance['settings']['title_value']) &amp;&amp; isset($instance['settings']) &amp;&amp; isset($instance['settings']['title_value']) &amp;&amp; $prior_instance['settings']['title_value'] != $instance['settings']['title_value']) {


But as you can probably see, that if statement is now twice as big. And since it's only a notice you're receiving, chances are the developer(s) won't put that issue as a top priority.

The easiest way to resolve the issue on your own though is to set the value of error_reporting to E_ALL &amp; ~E_NOTICE inside your php.ini file, like so:

error_reporting = E_ALL &amp; ~E_NOTICE


That should suppress all notices that you might be seeing, including the third notice regarding unserialize.

Hope that helps... :)