RaMBaM MAssuros 4:4 rules that a Nefel is Neveilah [MMishneh explains this is known from Chullin 75a - although he says in MAssuros 7:1, it is self evident]
If it is Neveialh then it ought not be Assur to eat as BBChalav, as Ein Issur ChAIssur - yet RaMBaM MAssuros 9:7 Paskens that it is.
meir rabi, melbourne australia
Regarding Question 1:
1) A very similar question to yours is asked by the Ma'aseh Roke'ach (cited by the Frankel edition of the Rambam in Sefer ha'Mafte'ach).
2) The Ma'aseh Roke'ach writes that he does not know why the Magid Mishneh writes that months are only required for the prohibition of forbidden fat, in the Sugya in 75a. The Ma'aseh Roke'ach writes that the reason why it seems that it is not necessary to mention this is that in the seventh chapter of Hilchos Ma'acholos Asuros, the Rambam never mentions any distinction concerning the number of months that had passed by, when discussing either the meat of the Nefel or the Chelev of the Nefel.
3) This question seems to be essentially the same question as yours, Meir, because the Ma'aseh Roke'ach's question is why did the Magid Mishneh mention the Sugya of 75a in 4:4, while in 7:1 he makes no mention of 75a, which means that it is self-evident that it makes no difference whether or not the full term of months has not been reached. The Magid Mishneh in 7:1 is following the Rambam there who made no mention of months, so the question is why did he mention months in 4:4?
4) The Ma'aseh Roke'ach concludes "v'Yesh l'Yashev" -- "it is possible to answer [this question]." The Ma'aseh Roke'ach does not tell us what the answer to the question is. He leaves us with some work to do, BS'D. However, it is comforting to know that the Ma'aseh Roke'ach writes that it is a question which has an answer.
Regarding Question 2:
a) The Rambam (Hilchos Ma'achalos Asuros 9:7) writes that if someone cooks a "Shalil" in milk or eats it, he is liable for cooking or eating meat with milk. The source of the Rambam is the Gemara in Chullin 113b which states that the word "Gedi" comes to teach that the Isur of Basar b'Chalav also applies to a Shalil.
b) However, the above Gemara is not a contradiction to the rule that Ein Isur Chal Al Isur. This is because a Shalil is not an Isur, but is in fact permitted to eat. Rashi writes in Chulin (89b, DH v'Noheg) that a Shalil is a live nine-month-old fetus found in the womb of the slaughtered mother. The Mishnah (Chulin 74a) states that if one slaughters an animal and finds a nine-month-old baby in the womb, according to the Chachamim (who the Halachah follows) the Shechitah of the mother is effective to make the "Shalil" permitted to eat.
c) Therefore, Shalil is permitted meat, and this is why the Gemara (113b) and the Rambam (9:7) state that one is liable for Basar b'Chalav for cooking or eating a Shalil with milk.
d) A Shalil is not similar to a Nefel. A Nefel is a baby which cannot survive, while a Shalil is a perfectly viable baby.
Kol Tuv,
Dovid Bloom