2-2 is the best answer; 2-3 is OK, but a bit clunky. The others don't work.
All the questions among the 3's are OK, but I'd remove the comma after "Then" in 3-2.
1. What was the old man’s lie?
2. You promised me a bag of gold.
2-2. It was that you promised me a bag of gold.
2-3. It was you promised me a bag of gold.
2-4. It was, you promised me a bag of gold.
2-5. It was, "You promised me a bag of gold."
[Which answers are suitable?]
3. Finally, what did the old man do?
3-2. Then, what did the old man do?
3-3. After the conversation, what did the old man do?
3-4. After he said that, what did the old man do?
3-5. After talking with the king, what did the old man do?
4. He walked away with a golden apple in his hand.
[Which questions do people usually use?]
2 answers
1, 2, and 2-2 are suitable. 2-3, -4, and -5 are not. 3-2 is wrong (no comma after "then"), otherwise all in 3 are okay. 4 is fine.