According to Beveridge's definition, which is perfectly acceptable to use in the exam, full employment is when 3% or less of the labour force is unemployed.
According to the free market definition, full employment occurs when ASL = ADL
PPF and LRAS. This is because when there is no spare capacity, all workers willing and able to work are working.
It does not mean that all members of the working population are in employment, frictional and structural unemployment is always occurring.