I think you could get it working with category__and

I remember trying a similar approach to yours and found out that I would get content that was either in platform and/or in review. But to get actually posts that where only on both, excluding posts that were just in one of them, this was my approach. Maybe the way you have your posts works with that approach, but it didn't with mine (which was more like city / type of event / cost of the event).

Anyway, you could pass your combination of elements through POST, and then on the receiving page get those elements into the array:

$myFilteredArray = array();
if (isset($_POST['.... 
// Do what you need to get the POST variable elements
into the array

// and then, use this query format
query_posts( array(
            'category__and' => $myFilteredArray, 
            'orderby' => 'title',
            'posts_per_page'=>-1, 
            'order' => 'ASC')
            );   

I think you could get it working with category__and

I remember trying a similar approach to yours and found out that I would get content that was either in platform and/or in review. But to get actually posts that where only on both, excluding posts that were just in one of them, this was my approach. Maybe the way you have your posts works with that approach, but it didn't with mine (which was more like city / type of event / cost of the event).

Anyway, you could pass your combination of elements through POST, and then on the receiving page get those elements into the array:

$myFilteredArray = array();
if (isset($_POST['.... 
// Do what you need to get the POST variable elements
into the array

// and then, use this query format
query_posts( array(
            'category__and' => $myFilteredArray, 
            'orderby' => 'title',
            'posts_per_page'=>-1, 
            'order' => 'ASC')
            );