Answer: R. Yehudah himself permits l'Chatchilah; Beraisa #1 is like his Rebbi, who says that b'Di'eved one was Yotzei:

(Beraisa - R. Yehudah citing R. Eliezer ben Azaryah): One must read Keri'as Shema audibly to his ears, for it says "Shema" - Mashmi'a (make heard);

R. Meir says "Al Levavecha" - it depends on intention in the heart.

We may now rebut Rejection #3:

R. Yehudah holds like his Rebbi (one is Yotzei b'Di'eved); R. Yehudah brei d'R. Shimon ben Pazi holds as R. Meir, who permits l'Chatchilah.

(Mishnah): R. Yehudah permits a child.

(Beraisa - R. Yehudah): When I was a child, I read in front of R. Tarfon and other Chachamim.

Chachamim: We may not bring a proof from what one remembers when he was a child.

(Beraisa - Rebbi): When I was a child, I read in front of R. Yehudah.

Chachamim: This is no proof, he is the lenient opinion!

Question: Why didn't they respond that we cannot bring a proof from childhood?

Answer: A second rebuttal was given; they rejected his proof for both reasons.

(Mishnah): The following should be done only after sunrise:

Keri'as ha'Megilah, circumcision, Tevilah, Haza'ah (sprinkling water on which ashes of Parah Adumah were put), also the Tevilah of a Shomeres Yom k'Neged Yom (a woman who saw blood during one or two of the days of Zivah).

If any of them was done after dawn, it is Kosher.

(Gemara - Question): What is the source (for Keri'as ha'Megilah)?

Answer: We learn from "These days ...."

Suggestion: Our Mishnah refutes R. Yehoshua ben Levi, who said that we must read the Megilah at night as well!

Rejection: No, the Mishnah teaches about the day reading.

We learn that circumcision is by day from "On the eighth day".

We learn about sprinkling from "On the seventh day". Tevilah is equated to sprinkling.

Question: Why was it necessary to teach Shomeres Yom k'Neged Yom separately from others that are Tovel?

Answer: We would have thought it is like the first sighting of a Zav (a man who had emissions from his Ever), which is compared to a Ba'al Keri (one who had a seminal emission);

A Ba'al Keri may be Tovel the same as the emission. A Shomeres Yom k'Neged Yom cannot do so, for it says "Kol Yemei Zovah k'Mishkav Nidasah Yihyeh Lah" (this obligates Shmirah, i.e. to wait one day (without blood) before Tevilah. A partial day is considered like a full day);

Had the Mishnah not taught Shomeres Yom separately, we would think that Shmirah of the start of the coming night would suffice, and she could be Tovel at night.

The Mishnah teaches that this is not so. She must count (a clean day), and counting must be by day, therefore she cannot be Tovel until day.

(Mishnah): If any of these was done after dawn, it is Kosher.

Opinion #1 (Rava): We learn this from "Va'Yikra Elokim la'Or Yom" - from when it is Me'ir (illuminates) is called day.

Objection: If so, we should similarly learn from "Vela'Choshech Kora Laylah" that night begins when it starts to get dark, but we hold that night does not begin until Tzeis ha'Kochavim (when stars are visible)!

Opinion #2 (R. Zeira): We learn from "We work ... from dawn until Tzeis ha'Kochavim" and "We watched at night, and worked by day."

Question: Why is the second verse needed?

Answer: We might have thought that they worked extra, even before the start of day.

(Mishnah): The following may be done any time during the day:

Keri'as ha'Megilah, reciting Hallel, blowing the Shofar, taking the Lulav, and Tefilas Musaf;

Korban Musaf, Viduy (confession) over the bull (of Yom Kipur), Viduy Ma'aser, (an individual's) Viduy on Yom Kipur;

(The following Avodos of Korbanos -) Semichah (pressing on its neck), Shechitah, Tenufah (waving); Hagashah (bringing a Minchah close to the Mizbe'ach); Kemitzah (taking a handful of a Minchah); =Haktarah (burning on the Mizbe'ach); Melikah (killing a bird by pinching its neck); Kabalah (catching blood in a Kli Shares); Haza'ah (sprinkling blood on the Mizbe'ach);

Hashka'as Sotah (making a Safek adulteress drink the water that tests her), Eglah Arufah (beheading a calf to atone for an unknown murder), and Taharas Metzora.

The entire night is Kosher for reaping (barley for) the Omer, and Haktarah of Chelev and limbs.

Any daytime Mitzvah is Kosher all day; a nighttime Mitzvah is Kosher all night.

(Gemara): We learn that the Megilah is read by day from "These days are remembered."

We learn about Hallel from "From the east (rising) of the sun until its setting";

Rav Yosef says, we learn from "This is the day that Hash-m made."

We learn about Lulav from "You will take on the first day."

We learn about Shofar from "Yom Teru'ah."

We learn about Korban Musaf from "Devar Yom b'Yomo". Chachamim enacted Tefilas Musaf to be like the Korban.

We learn about Viduy over the bull from a Gezeirah Shavah "Kaparah-Kaparah" from atonement of Yom Kipur, which is learned from "On this day to atone for you."

We learn about Viduy Ma'aser from "This day Hash-m commands you."

We equate Semichah to Shechitah, and we learn Shechitah from "B'Yom Zivchachem."

We learn Tenufah from "B'Yom Hanifchem". Hagashah is equated to Tenufah.

We learn about Melikah, Kemitzah, Haktarah and Haza'ah from "B'Yom Tzavoso (... Lehakriv Es Korbeneihem."

We learn about Hashka'as Sotah from a Gezeirah Shavah "Torah-Torah" from judgment, which is during the day.

(D'Vei R. Yanai): We learn about Eglah Arufah from Korbanos. Regarding both of them it says "Kaparah".

We learn about Taharas Metzora from "Ba'Yom Taharaso."