A percentage is a pure number: it has no measurement units.
yes, it is. The smaller the measurement, the higher the percentage error.
what is the number supposed to be if you git 7 cm? Percent error is the percentage that you're incorrect by, so you need another measurement. to do it, you find the difference and then divide by the original so (7-x)/true value then multiply by 100 to get percentage.
The answer may depend on why the measurement is changing.
there is no difference between units of linear and perimeter measurement.
It depends on what is being measured, and the unit of measurement you will be using.
Saturated percentage of oxygen (SpO2) is a measurement of oxygen levels in the blood
Miles are a measurement of distance, a knot is a measurement of speeed.
Volume is a measurement of capacity. Dimension is a linear measurement.
A kilometre is not a cause, it is a measurement unit for distance.