Citi Junior Developer interview questions

HR rep called and scheduled the interview.My profile did not match completely, but I was given a phone interview. There were three interviewers - Project Manager and Two developers. Project manager explained the product they are developing.

Got an email from HR to set up a time to speak. I said anytime except for 1.5hrs during the day. They chose to call during that time slot. Technical interview with hiring manager was set up after that. The technical interview main question was to figure out what's the probability of getting a specific four digits out of 800 digits. A few days later I was asked to come in for an interview where I was to meet with three people. Some of the questions were "What is the most important stage in the SDLC?" or "How is CSS using advantages of OOP?"