Welcome to your interview.
The question is on your right: Most Challenging Project and Learning. Take a moment with it first.
Talk your thinking through with me if you like - when you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes). Discussion and graded submissions share your five interviewer interactions, so spend them well.
What is the most challenging project you have worked on, and what did you learn from it?