Why did Hashem repeat Chazak ve'Ematz?
Rashi: Strength yourself in Torah
What is "Taskil"?
Rashi: You will succeed. 1
Malbim: All Mitzvos of the Torah have a purpose
Why must it say "Asher Tzivcha Moshe Avdi"?
Malbim: You should fulfill due to the Torah's command, and not due to your intellect's conclusion.
From what may you not veer?
Radak #1: From Moshe, i.e. his good ways.
Radak #2: It is from the Sefer Torah, even though the verse mentioned only the Torah itself.
What is "Yamin u'Smol"?
Malbim: Yamin is to add to the Torah, and Smol is to detract from it.
Why does it say "b'Chol Asher Telech"?
Malbim: Even those laws of etiquette based on intellect, which bring benefit, encompass only general rules, but not every detail of conduct. Mitzvos of the Torah teach the correct path in all ways.