These are just my *opinions* only from my experience dealing with trauma victims. I am not a forensic pathologist. And I am speculating only, as all sorts of weird and unpredictable things can happen with the human body, and it is impossible to know all the variables that may affect potential injuries in certain situations.
Saying all that, here goes:
1. I have discussed this very question with colleagues. IMO, it is possible that there would be no blood with a child falling from a balcony 5m high. Injuries that would cause a death, without obvious blood seen externally, from such a fall would be a C-spine fracture, traumatic brain injury, or even, but probably less likely, a ruptured internal organ such as spleen/liver. And to answer a question from a previous thread, it is possible to suffer a traumatic brain injury without presence of a skull fracture, although I would hazard a guess that head injury sustained by a child falling 5m would be found in conjunction with a skull fracture (that may or may not be in conjunction with a scalp laceration - which do tend to bleed a lot).
2. and 3. Falling from a height of 5m would most likely not be survivable for a small child. Whether a child would be conscious or not after a fall would depend on the injury responsible for cause of death, but if the fall was fatal (as I think would most likely be the case), the severity of the injuries sustained would mean that the child would not be conscious for very long (if at all).