For the phone interview, the interviewer asked mostly why I wanted to apply for the position, why I was a good candidate, and my general role of my current job. The interviewer explained details of the position and confirmed with me whether I still wanted the position.
Two days later the HR called and confirmed again of my interests, and told me in great detail of the hiring process and my next interview. Try ask more questions about the interview, the interviewers, possible questions. My HR is extremely helpful. The two phone calls are all cold calls, u can ask them to call at a later point as a strategy.
The three interviews through Hangout happened a week later, the questions are mostly behavioral questions, a couple brain teasers, and some business strategy questions. I searched standard questions and answers online (Glassdoor helped a lot) for both and I was well covered. For the last type of questions, there're no standard answers, stay calm and treat them as school projects.