The reason why I don't think the top "thing" is nub is because it appears to go up into the stomach on the most superficial of levels. That seems to indicate cord to me. Now, if that WAS part of the nub, that could be a vulva but it just seems up too high and too prominent.
I think where the yellow arrow is ~may~ be nub but the nub really should extend a bit farther than that. It could also be leg bone or even a finger, tho I do think I see the arm in a different place.
That's not stacking. Not in the right place and do you see how the "bulb" looking thing seems attached to the stomach? My guess is cord, nub, then leg bone but I can't be sure these are just too grainy and not complete enough

