FeatureX Software Engineer interview questions

I just finished the first two steps of the interview process. You may talk to the CTO on phone first, and preschedule a 4-hour programming test at the same time. After talking with CTO, they will determine to take programming test or not. The CTO is a very kind person and the talk is pretty relaxed. Programming test is proctored via email, and there is only one problem to solve but may take several hours. I am waiting for next step.