1 Is the only thing that separates Suse from some other distos its unique YAST option where you can configure Linux with ease?
Yes, it is extremely easy to configure for users that have little experience with linux. YAST is basically the tool that seperates the user from the text based configuration that most linux distros use.
2. Is Yast for Suse like Control Centre for Mandrake where you can through graphical interface edit linux settings instead of editing them through the old fasion way by editing the config text files or through the console?
No, control centre is part of KDE (Maybe Gnome too), Control centre it still in SUSE however there also the YAST modules in there as well.
3. could you intsall YAST on other linxu OS's like Red Hat?
NO, I think SUSE have commercial rights over YAST
4. What's the diff. btwn Linuxconf, Gnome System Tools and Webmin? do they come on all linux distros? Are they any better than Yast?
There are totally different things, GNOME is a Window manager like KDE, fluxbox etc. You can install SUSE with gnome as the window manager if you want but I would suggest sticking withe the default KDE because I think it is easier to use. Webmin can be installed on any machine including SUSE, you can probaly get Webmin rpm through YAST online update.