Can Symbolic Links span different file systems in Unix or Linux ??? I.e consider different file systems like ext2 and ext3 can symbolic link span them?
I think you're confusing mount points and filesystem semantics.
The answer is yes though.
Symbolism has nothing to do with file systems or mount points.
Since a symbolic link is just a particular type of file containing a pathname, nothing prevents a symbolic link from pointing to something located on another filesystem. Nothing stops a symbolic link from pointing to something that does not exist at all.
$ ln -s 'hello world' link $ ls -l total 0 lrwxr-xr-x 1 myself wheel 11 Feb 20 08:08 link -> hello world
The filesystem type (ext3 etc.) is largely irrelevant. A filesystem that does not support symbolic links can not hold symbolic links but could still be the target of symbolic links.