Chicks will not hatch unless the egggs are kept at incubation temperatures for three weeks. Incubation temperature is around 99.5 Fahrenheit (37.5 C), plus or minus a couple of degrees.
However they can develop enough to notice when you crack them open even if stored at cooler temperatures. I've read that can be as cool as 80 F (27 C) but I don't put a lot of faith in that. I think that is someone being very cautious. Still I use 80 F (27 C) as my cutoff for storing fertile eggs because I just don't know for certain.
The eggs you buy at the store are electronically candled to make sure nothing is in them. It is not that unusual for eggs to have blood spots or meat spots in them, whether commercial eggs or our eggs. They don't want to upset customers so they candle to remove those eggs. They sell the removed eggs to places that don't need the eggs to be perfect, like maybe a pet food manufacturer. When you see something like that in your eggs it has nothing to do with a rooster.
Because of blood spots and meat spots I consider it a good idea to open out eggs in a separate bowl before mixing them. You can get some surprises.