On the plane, the four points form the shape below
Notice that it is a parallelogram.
1) Since it is a parallelogram, AD=BC and AB=CD. Using the formula for the distance between two points on the plane,
Then,
Therefore, the dimensions of the yard are sqrt13, 5 or 3.605551..., 5
2) The perimeter is
The perimeter is 17.211102 units or 2sqrt13+10
3) As stated above, it is a parallelogram