Mary has given you some very good advice and ideas. I will add a little to what she said.
1) What I think you are trying to do, let students work offline, would be very difficult. Moodle is designed to be used over the Internet. In my world travels (Italy, France, Mexico, Canada, US, China), there has always been an Internet connection. However, I can appreciate that there are probably many places in the world without an Internet connection.
2) As Mary said, not easily. No.
3) I do this in my Moodle. I use the Formal White theme, and I had to add some custom CSS code within the Formal White configuration. Very simple.
a:link { color: #990000;}
a:visited { color: #cc6666;}
Many themes allow you to add custom CSS code.
4) Mary is right on!
Hope this helps you.