Answer to 1st question: They dug irrigation systems and canals to get the water to their crops.
Answer to 2nd question: They knew how to boost the immune system and they knew how to get the body to produce more white-blood cells. They also had a 90% success rate on surgeries, including brain surgeries.
Answer to 3rd: He had a big army and long roads leading all over his empire so if there was an uprising his army could travel quickly.
Hope this helps, have a good day. c;
