It's very easy for ETS raters to identify memorized responses because they sound different and the content is different from responses that are more natural and spontaneous.
Don't try to write a full response because you won't have time, and the rater scoring your response want to hear you speaking, not reading, and they can tell the difference.
I see a lot of students make this mistake: they want to impress the TOEFL rater so they use vocabulary that's very advanced but they don't use it correctly.