3. Is there a dependent and an independent variable?

Yes, there are clearly identified dependent and independent variables, so that a regression is appropriate.
 The data are parametric: Linear regression (other models could also be used)
 The data are nonparametric: Nonparametric regression models are not covered here

No, the variables are interdependent and a test of correlation is appropriate.
 The data are parametric: Pearson correlation
 The data are nonparametric: Spearman correlation