I know almost nothing about tap (understatement), so sorry in advance for the probably very silly questions about the shoes. 
I just wondered what age heel taps are recommended for. Also, why heel taps are available to buy separately, and should horseshoe or full heel be purchased. Do heel taps fit any tap shoes, or do those have special holes in the heel. Also wondering if heel taps are compulsory for exams.
Any other advice appreciated. DC's first exam at the end of this month.