JUSPAY Software Engineer -2 interview questions

I applied through a employee referral (Juspay, Bangalore), recruiter sent me a coding challenge on talscale after completion I received another coding challenge on hackerearth followed by a phone call screening, later recruiter informed me I am shortlisted and asked me if I can participate in 2 days Hackathon, when I asked recruiter that I have already taken two online test she responded saying only one was meant to send, two were sent by mistake. (which here was red flag one) 2 day remote Hackathon setup included slack and google meet, Juspay created a slack setup for all applicants, there were two rooms one common room with all other participants and company employee and one personal room with you and company employee : day 1 started with 1:30 minutes introductory session from founder of the company on a hangouts calls in which they pretty much described all projects they have. followed by a common problem for around 24 participants and problem was sent in common slack room, no specified time limit, or any other instructions (other than you can talk to your interviewer in your personal channel) were given. we have to solve the problem and communicate via slack in our personal room, (there were no phone call/ video call whatsoever ) and suddenly in the middle of Hackathon recruiter messages on slack channel you can submit your first part of problem before lunch (which was also not mentioned before). The only mode of communication with interviewer was slack. I completed my code and submit both the parts before first break, but interviewer kept on arguing about implementation they wanted to see (on slack, nobody proposed to have a call // and there were multiple people talking to you at same time with their own different views). The method they wanted me to implement was highly inefficient, I gave them multiple examples how that idea was a big failure, and they just stopped replying on chat. I tried asking them multiple times "let me know what you think about it". they just stopped replying. And after sometime recruiter just called saying sorry you are not shortlisted even before the Hackathon was finished, she did not even had a valid reason to tell me why. which was absurd. The whole process has so many flaws and lot of time waste.