Understanding Moses' four-fold way of study (Eruvin 54b)

Question

Following my previous question "what-were-the-pieces-of-moses'-transmission", I wondered:

1. where this form of study was learned from?
2. what were the benefits of this form of learning?
3. if the content wasn't different, wasn't it more efficient to study 4 times all together instead of 8 times?

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The source (Eruvin.54b):

The Sages taught the baraita: What was the order of teaching the Oral Law? Moses learned directly from the mouth of the Almighty. Aaron entered and sat before him, and Moses taught him his lesson as he had learned it from God. Aaron moved aside and sat to the left of Moses. Aaron’s sons entered, and Moses taught them their lesson while Aaron listened. Aaron’s sons moved aside; Elazar sat to the right of Moses and Itamar sat to the left of Aaron... The elders entered and Moses taught them their lesson. The elders moved aside, and the entire nation entered and Moses taught them their lesson. Therefore, Aaron had heard the lesson four times, his sons heard it three times, the elders heard it twice, and the entire nation heard it once.
Moses then departed to his tent, and Aaron taught the others his lesson as he had learned it from Moses. Aaron then departed and his sons taught the others their lesson. His sons then departed and the elders taught the rest of the people their lesson. Hence everyone, Aaron, his sons, the elders and all the people, heard the lesson taught by God four times.

Answer 1

The Gemara a little further on asks two questions about this process;

וְלִיגְמְרוּ כּוּלְּהוּ מִמֹּשֶׁה! כְּדֵי לַחֲלוֹק כָּבוֹד לְאַהֲרֹן וּבָנָיו, וְכָבוֹד לַזְּקֵנִים.

With regard to the manner in which the Oral Law was taught, the Gemara asks: They should all have studied from Moses himself four times. The Gemara answers: The teaching was divided in this manner in order to give honor to Aaron and his sons, and also to give honor to the elders.

וְנֵיעוּל אַהֲרֹן וְנִיגְמַר מִמֹּשֶׁה, וְלִיעַיְילוּ בָּנָיו וְלִיגְמְרוּ מֵאַהֲרֹן, וְלִיעַיְילוּ זְקֵנִים וְלֵילְפוּ מִבָּנָיו, וְלֵיזְלוּ וְלַיגְמְרִינְהוּ לְכוּלְּהוּ יִשְׂרָאֵל! כֵּיוָן דְּמֹשֶׁה מִפִּי הַגְּבוּרָה גָּמַר, מִסְתַּיְּיעָא מִלְּתֵיהּ.

The Gemara asks why a different method was not adopted, one which would have involved less trouble for Moses: Aaron should have entered and studied from Moses; his sons should then have entered and studied from Aaron; the elders should then have entered and studied from Aaron’s sons; and then they should have gone out and taught all of the Jewish people. The Gemara answers: Since Moses had studied directly from the mouth of the Almighty, it would be more effective for everyone to hear the Torah at least once from Moses himself.

The Maharsha says that the process of who went first, second etc. was learned from the setup on Har Sinai where Hashem said Aron goes Higher than his sons who go higher than the Elders who go higher than the rest of the nation.

משה למד כו' נר' שסמכו דבריהם אקרא דפרשת משפטים ויעל משה ואהרן נדב ואביהוא ושבעים מזקני ישראל כסדרן בקרא כך סדר למודן וכל המוקדם בפסוק נכנס בתחלה וכדמסיק כדי לחלוק כבוד כו'. ואמר

The Ben Yoadah on the Gemarah says that the reason all Klal Yisroel did not just hear it 4 times from Moshe was because it was too much to teach it to 600,000 at one time. Doing it more than once would be too much for Moshe. Therefore Moshe did it once, Aron did it once, and so forth.

ובזה ניחא לתרץ קושיא אחריתי, השתא דמשני כיון דמשה רבינו ע"ה למד מפי הגבורה מסתייעא מילתא תחזור קושיא ראשונה לדוכתא, שיכנסו כולם בבת אחת וילמדו ממשה רבינו ע"ה? כי מאחר דמסתייעא מילתא טפי לא משגחינן בעבור הכבוד! וכפי האמור ניחא, דבזה האופן צריך דמשה רבינו ע"ה ילמד את כולם וישמיע קולו לכולם ארבעה פעמים, ואיכא בזה טרחא טובא

The Maharsha adds that only on the fourth time is it called Lishmah.

ונמצא ביד אהרן ד' כו' דאיתא במדרש דמשה נמי למדה מפי הגבורה ד' פעמים דכתיב אז ראה ויספרה הכינה וגם חקרה וגו' וענינו נראה שאחר שנתחזק להם הלימוד בג"פ יהיה לימוד הד' לימוד אמיתי לשמה וע"פ מה שכתבנו במסכת נדרים שהלימוד שלא לשמה הוא בג' דרכים והד' הוא לימוד לשמה והסימן שלהן אגד"ל שאלו ד' אותיות יש להן למ"ד ובג"פ יצא מכלל ג' לימוד שלא לשמה שיהיה להם הלימוד הד' לשמה:

So perhaps we can now answer all your questions.

1. It is learned from the set up on Har Sinai
2. It gave proper honor to those who deserved it - Kavod Hatorah, plus it gave everyone a chance to learn it 4 times and to hear it from each person on their 4th time which is the time of Lishmah.
3. It would of been too much tircha for Moshe to do it 4 times for the whole nation at once. All other options of teaching it are problematic based on the Gemarah's explanations.