Answer:
Hey there!
3) Well injection is usually done through the vein because they need the substance to go into the blood.
4) Some people believe that the heart is on the left side because its the left ventricle and atrium responsible and when people hear left they think the heart is on the left.
5) People living in high altitudes don't get as much oxygen so their bodies evolved into carrying ,more RBC so more oxygen is carried into their bodies.
Hope this helps :)