Jenny and her husband live in a society with a adventure park in the shape of a quadrilateral \(ABCD\). There are lamp post at the boundary of the adventure park and an entry gate is at point \(P\), the midpoint of side \(BC\). A path runs diagonally from corner \(A\) to corner \(C\). The gardeners have to set up a water sprinkler system, and the four sprinklers are located at points \(P, Q, R, S\), which are the midpoints of the sides \(BC\), \(CD\), \(DA\) and \(AB\) respectively.
Based on the above scenario, answer the following questions:
1. If the the four sprinklers at \(P, Q, R\) and \(S\), what kind of quadrilateral is formed by \(PQRS\)?
2. If the adventure park \(ABCD\) is a rhombus, what kind of quadrilateral is formed by joining the midpoints \(P,Q,R,S\)?
3. If the length of side \(AC\)(the diagonal of the adventure park) is \( 12m\), what is the length of the line segment \(PQ\)?
4. If the quadrilateral formed by the sprinklers \(PQRS\) is a rhombus, what special property must the diagonals of the adventure park \(AC\) and \(BD\) have?
4. If the quadrilateral formed by the sprinklers \(PQRS\) is a rhombus, what special property must the diagonals of the adventure park \(AC\) and \(BD\) have?