The ISO length unit to use would be the cementer.
Centimeters.
foot
Foot
Metre or foot and inches
foot is the most precise way to measure any unit
the units that are used to measure a foot are meters and inches.
A square unit is a measure of area, a foot is a linear unit. There are no area units in any linear measure.
Vertical Foot
If you mean measuring the height, that would be expressed in meters.
Square Foot
There are many units of measure smaller than a foot. In standard US measure 12 inches equal one foot.
This cannot be answered since a linear foot is a measure of length while a square foot is a measure of area.