So…we’re not going to do your homework for you. If you have specific questions about R, or ggplot2 I’m sure folks would be happy to help.
As a starting point: diamonds is a dataset that comes with R, simply typing “diamonds” in the R console will show you the dataset. Try that, look at the variables available and want form they take, and think about what you need to do to answer these questions.
If you’re totally new to programming, there are any number of tutorials that should get you from 0 to answering these questions in a night, I’d suggest looking at offerings from Datacamp or Codeschool.