Few questions about Form_Validation

[eluser]jotorres1[/eluser]
Hello all, new here to the community. I was wondering if there is a way to know if errors exists within form_validation.

For example, I would like to be able to do something like this:

Code:

<?php if(validation_errors() == true):?>
<ul>
  <li>&lt;?php echo form_error('username'); ?&gt; etc... </li>
</ul>
&lt;?php endif;?&gt;

Question 2, Instead of using:

Code:

<li>&lt;?php echo form_error('username'); ?&gt; etc... </li>

Would I be able to use this instead? for the previous example:

Code:

$this->form_validation->set_error_delimiters('<li class="error">', '</li>');

Q3, for the rules: Is it possible to use some native rules, and at the same time use a callback_ validation function?

Thanks!