Characteristics Limit?

Hi,

You shouldn't use characteristics for that. the characteristic system creates one variant per combination of values of the characteristics. If you have 4 characteristics with 34 values each, that's 34*34*34*34 variants. Way too much to be processed by a normal server.
Instead, you should use custom fields on the table 'item' (business version). The limitation is that it will be displaying for all the products in your store which might not be what you're looking for. In that case, you can always change a bit the code of the show file of the view product to display them only for the products where you need them.

In that file you have the line:
if(!empty($this->itemFields)){

Suppose that your product has the code "multi_pack", you can change it to:
if($this->element->product_code=="multi_pack" && !empty($this->itemFields)){

In the file cart of the view checkout, you can check the line:
if(hikashop::level(2) && !empty($this->extraFields)){

to:
if($row->product_code=="multi_pack" && hikashop::level(2) && !empty($this->extraFields)){

In the email you have the line:
if(!empty($itemFields)){
that you can replace by:
if($item->product_code=="multi_pack" && !empty($this->itemFields)){

In the invoice, the items custom fields are not displayed.

In the order page details on the front end and on the back end (file show and form of the view order), you have the code:
if(hikashop::level(2) && !empty($this->fields)){
that you can replace by:
if($product->product_code=="multi_pack" && hikashop::level(2) && !empty($this->fields)){

Yes. You should not have required custom fields on the table item if you hide them because the system will refuse the operation on pages where you hide them

So you want to display the custom field value only if there is a value in it ?

In that case you need to add the line below in the foreach displaying all the custom fields:
if(empty($product->$namekey)) continue;
after the line:
$namekey = $field->field_namekey;
for example in the file form of the view order.

In the order creation email sent to the user, you have the code:
if(!empty($itemFields)){
foreach($itemFields as $field){
$namekey = $field->field_namekey;
echo '<p>'.$fieldsClass->getFieldName($field).': '.$fieldsClass->show($field,$item->$namekey).'</p>';
}
}
which handles the custom item fields display.

That code is ALREADY in the email. So you should already see the custom fields.
Maybe you're using an old version of the email (the version number should be at the top of the email) ?

My code was an example...
As you can see, the product information comes from the variable $item in the email where that variable is called $product in other places.
So instead of using
if(empty($product->$namekey)) continue;
you should use:
if(empty($item->$namekey)) continue;