Adding category description to product description

You can have several categories for one product.
So you will have to edit the show file of the product view and load the category data with a MySQL query.

If you do your modifications with our interface in Display->Views, they won't be overwritten as we use the MVC standard of joomla and save your modifications in your template.

The best way to edit the hikashop CSS is to do it via the interface we have for that in the config under the tab display in the CSS area. That way, you won't loose your modifications when you update in the same way as with views modifications.

Not all the classes are defined in the CSS. That's because we only defined the CSS classes that needed some styling by default. So if you don't have any code for a class in the CSS you can just add it. Either in our CSS, or in your template.

This thread is about adding the category description on the product page. As I explained, it requires custom code. Something like this should do:
<?php
foreach($this->categories as $category) echo $category->category_description;
?>

The other thread is about adding the description of the current category on the products/subcategories listing page. That can be done by turning on the "show description" option of your menu via the menu Display->Content menus.