Online test with two problems on codility followed by three online interviews through hangout meaning. Questions was about algorithms, ds, and few behaviors questions. Be prepared for interviwers with english accent

Very Bad Experience- I was interviewed for SRE(Singapore). First round, it consists of two people interviewing for coding and system. Some basic questions from system and one coding challenge. This round is for about one and half hours. After this got a mail saying I have moved to the second round. I was given few free time slots to pick for next round. On the day for which I picked the slot, I was told that the slot is taken and will have to reschedule it. Selected a different slot and joined the zoom call on the new rescheduled date and time. After waiting in the zoom meeting call for 10 mins, I asked the HR over mail to look for the person if he is joining the call or not. With no surprise, the person who was supposed to interview me was busy and I was told to reschedule it again. After this I got a rejection mail saying that I am not experienced enough and did not give satisfactory answers in my initial round. Surprisingly they realised it after wasting my three weeks and moving to the next round. They don't tell you what the next round is about. No suggestions on what topics to refresh.