Ha'amek Davar: This teaches for future generations in exile, when they will be judged in front of their masters, they should not speak more than the answer to the question.
2)
Why does it say "ha'Od Lachem Ach"?
1.
Ha'amek Davar: The Hei does not introduce a question,
1
like "ha'Od Avichem Chai" (43:7). Rather, it specifies, "Why did you tell this matter?!"