Just a quick answer on your items
1) A sandbox issue.
2) Nope, the e-commerce group is purely optional. It's there already for future functionality. By default e-commerce is setup to allow only registered users to checkout, but this can be changed by a setting in the checkout widget.
3) A sandbox issue.
4) A sandbox issue.
5) Image upload works just like the default image upload in the general Sitefinity.
6) At the end of the checkout process, on the final step before confirmation (the preview) there are options to go back and change settings from previous steps. You can see it in sf-05.png (Ändern)
7) No, discounts are usable once per order, currently no functionality exists to limit them to once per user (since anonymous users are also able to checkout, this would be a custom thing).
8) Rounding to .05 instead of .04 etc, should be done with custom code (if needed everywhere) but can also be achieved by editing the formatting options of the templates (if needed just for cash payment).
9) The system displays the payment method, not the payment name by default, so offline payments don't get specified.
10) ...feature request...
11) ...feature request...
12) Correct, it's a 'bug' in the workflow/naming process. Currently Sitefinity expects first 'shipped' and 'paid' as the final flag meaning the order is completed. If you change the status to shipped, you basically tell it to go a step back.
13) See 12) pending is phase 1, shipped phase 2 and paid is phase 3 atm.
14) True it's a hardcoded 'continue', not yet localizable.
15) I'd say that's beyond the scope of the ecommerce package since it's not an order management system. Some shipping providers offer the ability for a tracking code though.
16) Reports aren't yet functional or multi-lingual/currency... Currently only displaying 'paid' orders in $.
17) Again, it's an ecommerce package, not an order management system. Deleting data is possible just like any other content item.
18) Sandbox issue. Order confirmation emails are send out in the regular version with all details present.
19) Sandbox issue.
20) On the order overview there's a 'print' button...
Most are sandbox issues and with regards to paid/shipped & pending status of orders, this is how they implemented the system atm unfortunately. Reports are a non-feature as they are currently implemented....