Sunrise is a line, 1/2 the length of earth's circumference. Sunset is a line for the other 1/2 length of earth's circumference. Sunrise lines and sunset lines are in constant motion. In reference to a location on earth.
No one knows the starting positions of these lines in reference to a location on earth. But they would have been 90 degrees of incident/normal sunlight. As they are now.
So the answer to where is the first sunrise, or sunset, would be, is 90 degrees of normal sunlight for both.