"Prompt" is a noun in this case. The definition in the Oxford English Dictionary is this (I've added asterisks to indicate the important part): "Something said or done to aid the memory; a reminder; spec. a word or phrase spoken to remind an actor, reciter, etc., of a forgotten word or line. Later also more generally: **anything which when seen, heard, etc., acts as a stimulus or guide to some action; a cue.**" A "prompt" on an exam is the "cue" that tells you what to do. For example, you may see an exam with a prompt such as "Write a two-paragraph essay describing your city," or "Analyze the poem below," or "Underline all of the adjectives below." These are "prompts" rather than questions, because they don't ask you a question. They tell you to do something. In some cases, an "essay prompt" is simply a topic for you to write an essay about. That's probably what the "topic prompt in Part 2" refers to. Part 2 will give you a topic to write about, and then you'll also have to have a more abstract conversation about the same topic.

No, here it is a noun. If I am acting in a play, I will wait to hear the line before my line, and then I will say my line. The line before my line is my "prompt". Now, "prompt" generally means "the thing that lets you know when to do the thing that you have been preparing to do." "When I was in a sword-fight with Bob, I wanted to make him tired before I began my real attacks. When I saw him start to sweat, that was my prompt, and I began to look for opportunities to actually beat him." "The school-bell was the prompt for the students to begin walking to their next class." Here, "topic" is acting like an adjective, and "prompt" is a noun. The examiner gives you your topic, and that is the prompt that tells you to begin speaking. EDIT: ninja'ed by Gray