Question: Here it connotes that regarding the open [Mem, i.e. not the final Mem], it says that Nevi'im said them;

In Megilah (2b), the Gemara challenges R. Chiya bar Aba from "Eleh ha'Mitzvos" - from now (after Moshe), a Navi may not change any [Torah] law. Also, Rav Chisda said that the Mem and Samech in the Luchos stood miraculously;

Inference: R. Chiya discusses the closed form (final Mem)!

Answer (Ri): There, it means as follows. Further, Rav Chisda said - i.e. further, if R. Chiya discusses the closed Mem, also Rav Chisda's teaching is difficult! Rather, surely R. Chiya discusses the open form.

Implied question: Why did [R. Chiya] say Menatzpech, unlike the order of these letters in the Aleph Beis?

Answer: Menatzpech connotes "Min Tzofim" (from prophets).

Question: Why did he mention these words? They were not in the Luchos!

Observation: In the Yerushalmi and Bereishis Rabah, it says that R. Eliezer and R. Yehoshua were among those children. This is unlike the Bavli (for R. Yehoshua ben Levi lived much after them).

Implied question (against the Yerushalmi and Bereishis Rabah): It says in Pirkei d'R. Eliezer that R. Eliezer did not learn Torah until he was mature!

Answer: It means that he did not engage in Torah until he was mature.

Explanation: It has openings to enter. If one comes to purify himself, they help him. They open an opening for him to enter, similar to above, that they leave for him an opening to enter through it.

Alternative text: According to those texts that say "if one comes to contaminate himself, they open for him", we must say that "they help him" is more than [just] opening.

Question #1: Why do we discuss when he intended to write Ches, and his intent was not fulfilled? Even if he intended to write one Zayin, and he wrote two Zayinin, he is exempt, like one who intended to throw two [Amos] and he threw four (above, 73a)!

Question #2: Similarly, this is difficult for the Beraisa brought in the Gemara. If he intended to write one letter, and he wrote two, he is liable. Why is he liable? Why is this unlike one who intended to throw two and he threw four?!

Answer: We discuss when he needed to write two letters, and they could be any two letters. Now, he intended for an Isur (for which one is liable), and his intent was fulfilled, and even so he is exempt, like the Gemara explains, because [the letter] needs crowns.

Question #1: Why do we discuss when he intended to write Ches? Even if he intended to write two Zayinin, and he wrote without crowns, he is exempt!

Answer: We discuss when he needed to write Ches for a bigger Chidush. Only when he wrote two Zayinin, which need crowns, he is exempt, but if he wrote other letters, which do not need crowns, he is liable, even though now [at the time he wrote the two letters] he intends for one (of the two letters he wanted to write).

Explanation #1 (Rashi): This is vitriol.

Rebuttal: [If so] why did R. Chiya call it something else, and not adopt the wording of our Mishnah?!

Explanation (R. Tam): Ben Stada that it says here was in the days of Papus ben Yehudah, who was in the days of R. Akiva, like is proven in Brachos (61b. The original, uncensored text of Tosfos proves that Ben Stada is not "Oso ha'Ish", who was a Talmid of R. Yehoshua ben Perachya, who was long before R. Akiva.)

Question: [This is difficult for] Rav Acha b'Ribi Yakov! Regarding Rav Chisda's teaching (Gitin 20a) that if a Get was not written Lishmah, and one passes a quill over [the letters] with intent Lishmah, R. Yehudah and Chachamim argue about this, for a Beraisa teaches [that if a scribe was writing a Sefer Torah, and he thought that he needs to write 'Yehudah', and he mistakenly omitted the 'Dalet', and then realized that he needed to write Hash-m's name, R. Yehudah says that he passes the quill over the letters, and is Mekadesh the name. Chachamim say, this is not an ideal writing of Hash-m's name]...

Rav Acha b'Ribi Yakov rejected [Rav Chisda's teaching]. Perhaps there [Rabanan disqualify] only regarding a [Sefer] Torah, due to "Zeh Keli v'Anvehu" (one must beautify Mitzvos), but regarding a Get, they agree [that it helps];

Summation of question: [According to Rav Acha's rejection], like whom is our Mishnah (which exempts one who writes on top of letters that were already written)?

Answer: Only regarding a Get that was written Lo Lishmah, all agree that the top writing is considered writing, for the latter writing fixes more than the first, for it makes it Lishmah;

However, when the latter writing does not fix anything, all agree that it is not writing. Our Mishnah discusses this, and it is like everyone;

Rav Chisda, who says here that our Mishnah is unlike R. Yehudah, holds like he taught there that R. Yehudah and Chachamim argue about a Get;

He understands that our Mishnah here discusses in every case, even when the latter writing fixes;

However, according to Rav Acha bar Yakov, you are forced to say that our Mishnah does not discuss in every case. It cannot discuss a Get.

Reference: In Menachos (57a), regarding one who put meat on coals and k'Grogeres was roasted in two places, one opinion obligates, and one opinion exempts;

The one who obligates holds that this is unlike writing on two walls of the house, for there, there is no Chisaron (shortcoming, that they need to be) brought close to each other, like (the way this is a Chisaron) here.