As the vast majority of pipe organs are custom designed there is no one, definitive answer. A small, hand pumped, table top organ ("or Portative") might have as few as 25 pipes - or two octaves. The...
Rene Magritte meant that it is an image of a pipe .
Ranks. Each "rank" has a unique name assigned to it.
by gradually heating it
It depends on the number of ranks. Typically, there are 61 pipes per rank for keyboard ranks and 32 pipes per rank for pedal ranks.