Here are the answers to your questions:
Question 1: If someone says they are "feeling under the weather," that is an example of:
Answer: An idiom
Question 2: “Just as a caterpillar transforms into a butterfly, we can grow and change through our experiences in life,” is an example of:
Answer: An analogy
Question 3: When someone refers to a difficult situation as a "Herculean task," this is an example of:
Answer: An allusion
Question 4: Which of the following sentences includes the 3 secret words we’ve encountered so far in Unit 6?
Answer: During the dynamic debate, diverse delegates delivered detailed opinions, demanding decisive actions and diligent discussions on important issues. (Assuming "dynamic," "diverse," and "detailed" are the secret words).
If you have any further questions, feel free to ask!