Check the skills occupation list (SOL) in border.gov.au

Here: https://www.border.gov.au/Trav/Work/Work/Sk...tions-lists/SOL

No need, you just need enough points.

If you have a job, you can get a working visa sponsored by your employer. You don't really care about the SOL if this is the route you chose

depends on what route you are taking... if you are able to get employment first, then you have another visa
most people apply first because normally employers will not look at your CV if you don't have a work visa

having your job in the SOL is just the first step... then you need to check if you have enough points
http://www.migrationdesk.com/threads/point...immigration.24/