dose the neomorph have the DNA reflex trait?

Not sure what you mean. Both neomorphs looked identical as adults. They looks different as they grow, and both were shown growing at different stages in the movie since they were not both born at the same time, so perhaps that is what you are seeing.

Ridley said something about the neomorphs being more vulnerable because of the human DNA, which is why they have soft skin like a human instead of a hard shell like the xenomorph version.

I can see what you are talking about, as far as i remember indeed it was hard to see the Spines on the Neomorph that came from Hallets Mouth, compared to the Spines on the back of the one that used them to break out of Ledwood.

So i can see your point, and its a nice theory, one that could be a good explanation..

However the Neomorph in the Wheat Field Attack had spines, but then again this could be Ledwoods and not Hallets Neomorph

I cant recall if its had and how large the spines on the latter one that crawled up the Cathedral had, because i only saw the movie 3 times at the Box Office.  But i would assume this was the one that attacked Rosenthal and so indeed had Spines.

from the Concept works though, i will assume they are supposed to all be the same/similar and so that both Neomorphs would have grown Spines.

yes I also see what u mean. iv only seen the film once and didn't get a good enough look at the 2nd neo that came out the throat to see if it had spines or not. if it didn't then I would wonder why

Do the promotional X-Rays help?  THey look a little bit different, but hard to tell if there are extra tentacles/tails/something wrapped around them.

don't really see anything. its more when they birth does the 2nd neo have the spines. maybe if it doesn't its perhaps due to the gestation period. maybe having sensed danger the second neo erupts at an earlier stage than the first

The second neo that burst out of Hallett's mouth did not have spines.

It did not appear to be as formed as the one that burst from Ledward's back.

could be that it emerged prematurely due to sensing danger?