What is the significance of the three kinds of loaves, bearing in mind that a Torah comprised four?
Rabeinu Bachye (citing a Midrash): They corresponded to the three who would remain alive to bring them (Aharon, Elazar and Isamar)
We can add that the four kinds of bread that comprised the Korban Todah correspond to the four who need to bring a Korban Todah, as the Oznayim la'Torah explains in Tzav, 7:12.
Seeing as there were ten of each kind of bread, why does the Torah write "Lechem" in the singular?
Oznayim la'Torah: Because there is no plural form for 'Lechem' in Lashon ha'Kodesh.
What is the difference between "Lechem Matzos" and "Chalos Matzos"?
Menachos (78b):Which is synonymous with 'Revuchah', and which we learn from from the Chavitei Kohen Gadol. See Sifsei Chachamim. The three types of Matzah mentioned here are synonymous with the three kinds mentioned in Tzav, Vayikra 8:26 (Rashbam).
They were also baked in an oven (Rashbam). See also Sifsei Chachamim who describes how the Revuchah was baked.
What is the difference between "Belulos ba'Shemen (in connection with the Chalos) and "Meshuchim ba'Shemen" (in connection with the wafers)?
Rashi: They poured oil into the former and mixed it whilst it was still flour (before baking it), whereas they smeared oil onto the latter 1 after they were baked.
What did they do with the left-over oil?
Sifsei Chachamim: According to some, it was given to the Kohanim to 'eat'; according to others, they continued smearing it until the oil was finished.
How many loaves of each kind of Matzos were there?
Rashi and Rashbam: Each of the three kinds of Matzah comprised ten loaves. 1
Which the Gemara in Menachos 76a, learns from the Lachmei Todah. See Sifsei Chachamim.
What species of grain was used to make the various kinds of Matzah?
Targum Yonasan: They used wheat-flour to make each of the three kinds of Matzah. 1
All Menachos were made of wheat-flour, with the exceptions of the Omer (on Pesach) and the Minchas Sotah, which were of barley.
How were the wafer-Matzos anointed?
Rashi: In the shape of a Greek 'Chaf; which is similar to our (regular) 'Nun'.
QUESTIONS ON RASHI
Rashi writes that the Meshichah was in the form of a Greek 'Kaf', like a Nun. Below (verse 36) he says that all Meshichos were like this, but in verse 7, he says 'also this was like a [Greek] Chi' (like an X, and so it says in Menachos 75a)!
Sifsei Chachamim (36): This is an abbreviation for Chaf Yevanis. (His text of Rashi on verse 36 was Chaf"Yud, like our text of Rashi on verse 7. - PF)
Daf Al ha'Daf (Menachos 75a): Rashi hold that he wrote (verse 36), that.all the Meshichos were like a Greek Chaf Texts of the Gemara, Rashi (verse 7) and other Meforshim were mistakenly 'corrected' to say 'Chai' or 'Chai Yevanis' via scribes who did not realize that it is an abbreviation. Rashi (74b DH k'Min) says that we call a Kaf Yevani 'Kai'. (Our text of the Gemara and Rashi is k'Min Chai'; perhaps it should be 'k'Min Chaf' - PF.)
Rashi writes that the Meshichah was in the form of a Greek 'Kaf', like a Nun. If it is like a Nun, why did Rashi (and the Gemara) need to compare it to a Greek letter?
Rashi ha'Shalem: Perhaps it is like a backwards Nun. 1
The Gemara in Megilah, 9b even permits writing Sefarim in Greek due to the beauty of its language.
Daf Al ha'Daf (Menachos 75a) elaborates on the many opinions of which Greek letters are discussed, and its shape. (However, in a popular digital version of the Sefer, there is gibberish in place of some of the Greek letters. Try to see the Sefer itself or a photocopy. - PF)