On #6, I remember doing an evening 'sysadmin' course many years ago with some friends. The class notes were for the previous major release of BSD than the one we were using, and the instructor was useless. When asked about a problem, he'd just stand there going 'hrm' until you figured it out.
The three of us learned more from trying to follow the class notes and figuring out our way past the breakages than from the actual structure of the class itself.
> The class notes were for the previous major release of BSD than the one we were using
The fundamentals should barely change from version to version (indeed: many command line tools under UNIX are decades old - which - of course - does not mean that they are bad). So if you learn them with the previous version, it should be really easy to get the small differences to the current version.
The three of us learned more from trying to follow the class notes and figuring out our way past the breakages than from the actual structure of the class itself.