As to whether these characters and other supposed Neanderthal characteristics which fall "cleanly" outside the modern human range can be seen in still younger Neanderthals (e.g. Amud 7 a 10 month old, Dederiyeh 1 a 19 month old, Engis a 3 year old, Dederiyeh 2 a 4 year old and Gibraltar 2 a 4 1/2 year old) is a current research question. A problem is that the middle part of the face is often broken.
Gib 2, Amud 7 have lower jaws which are "squared off" at the front and chinless like those of adult Neanderthals.
Quite possible that the development patterns of Neanderthals was quite different to that of modern humans.
Our development pattern is as such for an evolutionary reason i.e. part of a long selection process in which the behaviour manifest (menopause at average age 47 in females).
Ditto for what Neanderthals had.
Neanderthals had on average bigger brains than we do. Proportions of the lobes were different. Humans (= some hydrocephalics) can almost do without brains i.e. with only 35% of the average human amount. So the nature of the program not its size is what matters. Quantity is not quality as any programmer can tell you. In fact a large programme is sometimes gussed to be what it is i.e. sloppy programming. Ditto for computer viruses.
Economy in the productions of science (Henry James said that about art) is beauty too.
Darwinian principles apply to the HIV which is very successful and whose structure has be called beautiful.
No plans to bring Neanderthals back to life at present despite notices around here which say "NEANDERTHAL AND PROUD".
The best way would be to incorporate genetic material from the frozen body of a Neanderthal into a modern human material.
That such a find has yet to be discovered out there in the frozen tundra. (What are thought to be Neanderthal tools - i.e. Mousterian- are known from Krupovaya Gora in Russia which is only 60 Km from the Arctic Circle).
Let's see if Japanese scientists can incorporate mammoth genetic material into present day elephant !