Displaying Error onBeforeSaveEntry
Is this something that can be done with the Craft page when saving an entry?


In 2.2, there isn't an easy way.  In the upcoming 2.3 release, we added a $performAction property to the event, so your can do something like:

$entry-&gt;addError('attribute', 'MyErrorMessage');
$event-&gt;performAction = false;


And Craft will not save the entry and return to the edit entry page to display any validation errors.

You should post your second question as an entirely new question.