about the characteristics showing in the cart ...

This is about the characteristics showing in the cart and the final cart, I'd like to customized a bit the way it shows up ... when you've got a few characteristics it might be a bit messy .. I'd like to add </br> or "'" in which file is it made .. in which file is it made ?

We actually started to add an option for that.
If you use a really recent version, you can just go in phpmyadmin and in the hikashop_config table add an entry with the namekey being characteristics_values_separator and the value being the separator you would like.

yep working fine ... but ... there is always a 'but' it also adds my separators in title in the product/show.php ... I'd like to avoid that ... but still want it in my cart ... how can I do that ????

You would have to edit the file show of the view product and change the code to use the main product name instead of the variant name.

So replace:
echo $this->element->product_name;
by:
if(!empty($this->element->main->product_name)){
echo $this->element->main->product_name;
}else{
$this->element->product_name;
}

and:
echo $variant->product_name;
by:
echo $this->element->main->product_name;

fantastic