You would change the scale list to add or delete scales.

The list in and of itself affects nothing.  The scales, when applied to your viewports, affect the ratios.

Why would you change the ratio?  Really?  Why would you plot one drawing at a different scale than another?

Aliases.  Do you know what an alias is?  They are just keyboard shortcuts to commands.  It speeds up the day to day work of creating/editing a drawing.

Everything you asked about is covered in adequate detail in your Help files and/or the User Guide.  I suggest that you always look there first.  If you have any questions that are not answered by those two resources or need an example of something then come here and ask.  Show some initiative; employers like people who do.


Edited by John Connor - 17.Aug.2013 at 12:19