Thanks, Mark!
I did it!!!
Let's ROCK: it working!
And my snippet-help (hack source) for ALL!
Config module (in admin panel): "Featured", "Unanswered"
File: /modules/mod_recentdiscussions/helper.php
Search: if( $filter == 3 )
in this section locate:
. ' AND a.' . $db->nameQuote( 'featured' ) . '=' . $db->Quote( 1 )
. $stateQuery
. $groupByQuery
. $orderBy
. $limitQuery;
and replace (insert 2 lines in query):
. ' AND a.' . $db->nameQuote( 'featured' ) . '=' . $db->Quote( 1 )
. ' AND (a.`category_id` = '. $db->Quote(JRequest::getInt( 'category_id' ))
. ' OR a.`id` = '. $db->Quote(JRequest::getInt( 'id' )).' )'
. $stateQuery
. $groupByQuery
. $orderBy
. $limitQuery;