Hi,
1. Go in the menu My account>My subscriptions on our website and download the Essential edition install package that you purchased. Then, install it on your website and if you still have the problem, go in the Joomla plugins manager and enable the "HikaShop user synchronization plugin" and that will fix the problem.
2. That's only possible with the Business edition of HikaShop by creating custom fields of the table "order" (for the checkout) or of the table "item" (for the product page) via the menu Display>Custom fields. You can upgrade from the Essential edition to the Business edition on this page:
www.hikashop.com/extensions/upgrade-my-version.html