There are a lot of versions of Solaris:
Solaris (operating system) - Wikipedia, the free encyclopedia
Preceded by the versions of SunOS, some of which became Solaris.
SunOS - Wikipedia, the free encyclopedia
Nobody can know them all, so stick to modern versions.
The Number One Skill is is knowing how to recover from a total disaster - like the computer room being destroyed. If you cannot do this, you are not an expert.
On the training front the Solaris Systems Administration course give you a head start, but do the pre-requisite courses first.