Answer:
1. It's difficult to find out if someone is blood doping because the body has red blood cells. First the doctors get blood samples. Because the body constantly produces new blood, the blood that was stored shows that it is old with the blood samples it shows that there are some new and some old blood cells, which is how you can tell if they are doping.
2. Hemoglobin is a protein that is produced by the body that carries oxygen in the red blood cells the more red blood cells the more hemoglobin you have. Ex; If the athletes have a high level of hemoglobin on the day of the race than it had been days or weeks before, to shows that the athlete was blood doping.
3. It can help the body produce more blood cells to carry more oxygen (get more energy) and the body can get used to that kind of high altitudes and climates. Which leads to you getting even more energy at lower altitude levels.