Yes.
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Normally, none.
Vertical lines in space run perpendicular to the horizon. The very definition of perpendicular requires that the lines be at right angles to the horizon, so all lines that meet that definition are perpendicular.
Coplanar lines are when all the points sit in one plane. This is something that is commonly used in geometry.
Usually none, but all ten can be perpendicular.
It is possible for all nine lines to be perpendicular to at least one other line.