PlusMinusOne interview questions

The interview process lasted 1.5 months, and I completed all five stages. For the next two months, despite passing every interview, they kept making me wait continuously. They neither rejected me nor gave any feedback. Eventually, I found out they were keeping me as a backup while looking for someone willing to work for a lower salary. When I finally asked for a clear answer, they gave me a rejection. Very unprofessional.

4 stages. First, phone interview was unexpectedly quite technical. Second, I had to solve some personality quiz using an app. Then, coding interview and then case study. After passing all the stages I got declined without any explanation