Is there no way to save the systemdata on your harddisk ? (with knoppix live cd you can every time save what you changed)
I don’t think so. The objective of the openSUSE Live-CD is different from Knoppix. The openSUSE Live-CD is designed to give the user a taste of what openSUSE is like, in order to evaluate it for installation, and then if the user prefers, to do that installation.
live cd on it’s own is also useful, even without the installation on the HD.
Definitely. It’s just that openSUSE uses the live-CD as does Ubuntu or Fedora, really just for demo purposes. The installation DVD can be used for repair and rescue, as some live-CD’s are. But for a serious full-blown all-purpose live-CD, Knoppix or Kanotix are the way to go.