length
It doesn't matter.
They can come in any order.
Either doesn't really matter.
The width and the length are independent. You can have a very long rectangle which is very wide or not wide at all. They are related when it comes to calculating area or perimeter of the rectangle. Perhaps that is what you meant?
width always comes first
it is lxwxh (width x hight)
length
That particular style only comes in one width, Medium.
It doesn't matter.
You can do it whichever way is more convenient for you. The answer is the same either way.
After looking at several sites the rugs were all describe by the shorter(width) first.
The screen was about 10 inches long when it comes to the screen with of the microwave.
They can come in any order.
Either doesn't really matter.
When measuring a curtain, the length usually comes first. This refers to the vertical measurement from the top to the bottom. The width is then measured horizontally from side to side.
Stretch drywall is 54" wide, the width between the outer side beveled edges.