How I can hide module from custom Joomla group? I want module to be visible for registered users but hide it from paid 'premium' registered users.
You can create a new Access Level for your site, from here you can
control which users can view which objects on your site, like modules.
You can create your new access level in Users > Access Level
Now, assign to your user group the new access level, then that users
can view the modules assigned to this access level.