As far as I know, there are no “download access codes” for Steinberg software
How did you activate it. I assume you have purchased an e-Licenser dongle (even though you don’t mention one) Otherwise you wouldn’t be able to run it in demo mode either.
When you bought the software, you should have received an e-mail with a registration code. This should be entered in the eLicenser Control (eLC) application. (Download the latest version here: http://www.elicenser.net/en/latest_downloads.html ). A license will then automatically downloaded to your dongle. Just be sure not to jump the gun, but wait until eLC tells you that the license is installed. I assume that you’ve already done this, as you can run Cubase Artist in demo mode. I’ve never been asked for any “download access code” as part of the registration process.
Note that if you have installed a demo license and then install f full license, the demo license will be retained on the dongle. i.e. you will have two licenses on your dongle.
Are you sure that you have registered the full license, that you received with your mail, on your dongle?
This is a question that noone but yourself can answer. It all depends on your needs. What features you deem important. You’ll find a comparison chart here: