Draw the line with 'x' which connects the given points.
If the points are diagonal, a rectangle instead of diagonal line should be drawn

Regarding the points being diagonal, how can we verify this for a rectangle?

For a square, i.e. if the points are diagonal, we can verify with this formula:

|𝑥1−𝑥2|=|𝑦1−𝑦2|

this wouldn't apply for a rectangle