1 product but different code name and size

Hi,

Yes. You can use characteristics for that:
www.demo.hikashop.com/index.php?option=c...ow&Itemid=82&lang=en
www.hikashop.com/en/support/documentatio...html#characteristics

That's not possible. The "registration" option where you can select 'No registration' is only available in the commercial editions.

It's available in both the Essential and the Business edition.
HikaShop does not handle the express checkout of paypal but the standard paypal payment plateform.
Our commercial editions include all the features of the Starter edition plus additional features.
You can use the extension on other websites, yes.