If you look up hamburger and hamilton, you can find chicken stages of development. The pictures there should be similar to what all other birds go though, just in different periods of time. Features on the black spot can tell you how old it really got, as in, how well is the head formed, are there wing buds, leg buds, actual toes, feathers, and so on. Often, if the chick dies before the first week or so, it is due to a developmental or genetic defect. If the egg is scrambled, often it was just never fertile or died within the first day. Blood like we know it and can actually see, starts to form on day 2-3 in chickens, so probably early day 2 for the quail.