Review question

Draw a diagram showing points $A(-3,1)$, $B(4,2)$, $C(9,-3)$, $D(2,-4)$.
1. For the figure $ABCD$ state and prove a fact (or facts) sufficient to ensure that it is a parallelogram.
2. State and prove an additional fact sufficient to ensure that $ABCD$ is a rhombus.
3. Prove that $ABCD$ is not a square.