Yes, it is real. The construction material was different in different history periods and areas. The walls were mainly built of earth, wood and stones at first.

Yes, it is true. It can be seen from the ruins of the great Wall in Shanxi. The Great Wall was built according to local landform and before the Sui Dynasty, most of the walls were built in rammed earth, perhaps with wood pillar inside to make it more stronger and brich pavement to protect its outer side.