Can one upgrade from openSuSE 10.2 to openSuSE 11.2 upgrade or does one have to re-install the entire O/S?
Is this the same as for Novell’s SuSE?
Most certainly not.
Yes.
is there another one?
There have been so many changes since 10.2; for example, you now get a separate /home partition as the default and the filesystem is ext4 rather than reiser.
So a full back-up of your existing /home folder and mysql files will be needed before a fresh install. Given the changes, it is unlikely that many of the of configuration files you may have created for 10.2 will be relevant.