Hint (for Q1): Do you know the inductive formula for a determinant? A determinant of a 2x2 matrix [a b; c d] is ad - bc and you can use the inductive form to get det(A) for all matrices of higher order (i.e. rows/columns).
Take a look at the inductive formula here (if you don't have appropriate notes):
Determinant -- from Wolfram MathWorld