Recommendation: Stick to the script.
As a retired teacher, I prepared extensively for the 45-min. online demo lesson. The online ClassUp interviewer was positive and supportive, playing the role of an elementary student during the process. Unfortunately, I tried to be too creative, including some of my own materials (like a short video) and spending extra time to try to connect with the (role-played) student. In the end, I completed a little over a half of the "required" demo slides, and I am sure this doomed me.
The interviewer provided positive feedback at the end, but it was clear she had a points sheet based upon my performance for each of the slides/components of the lesson, and I am now convinced I did not receive the minimum number of points, even if I maxed the points for the slides that I did complete during the online lesson/interview time period.