Primarily logistical support and medical.
The same as white soldiers, to shoot and be shot at.
Yes, Black Soldiers did fight in World War 1
To kill and to break things.
The black soldiers were not treated or paid equally. At first the black soldiers were paid as laborers.
At first there were no black soldiers fighting for the union until later on during the war.
none, as black soldiers were only invented in 1921.