Hitachi Digital Services Interview Questions, Process, and Tips for Experienced

Interview preparation tips for other job seekers - Overall 3 stages: 1. With HR 15 min about you and CV and the job, 2. C++ Coding assignment to complete in an hour, 3. Technical interview in an hour, asking describe assignment, then answer question sheet about CPP and Python. In 3rd interview 2 people joined the online meeting. One Lead one Senior probably (though looking at their own profiles stuck in that position decades, if they were better engineers I believe they'd change to some better company).
For me they looked like proud and arrogant of themselves working in the company that shares famous Japanese name "Hitachi", though it's Hitachi Vantara founded in USA not Japan. They lack a simple politeness and respect to the opposite person which adds a bit nervousness. I cannot perform well even I know the topic enough if someone is looking at my work, and they force me to read loud the code fragment and try to debug it without debugger or compiler, guess what's the error in the code. After 3rd stage, 1-2 weeks later they rejected me without telling why. I knew very well that because of their attitude to me I was nervous and Yes, I did naive mistakes when harrying my answers, however they gave me no help on relaxing me, but making more and more tension, and I wanted to quit interview as soon as possible. Therefore, do not think they have culture from Japan like showing kindness. Very bad attitude towards my CV, though I receive from many recruiters my experience stands out as it has strong Computer Science education and multicultural environment experience.
I'd say for Junior position they ask more than typical Junior developer would be able to demonstrate. Anyone with more knowledge, or actually more preparations for interview questions would never apply to that far town somewhere in South West, Dorset of England and with that low salary barely reaching range of 35-40K.
After 3rd interview which was final, and they should've rejected or given an offer, I really wished won't pass, because I didn't like their attitude towards their company as they judged my CV with some sarcasm, then mentioned Hitachi and their Japanese colleagues with a bit of sarcasm of lacking English knowledge, about Japan as a country with different culture. Felt they are a bit racist or proud of being British, if I may call it.
I'm doubt if they as experienced software engineers would be able to answer deep CPP questions, or modern CPP otherwise why would they stack in that job over decades, and I know they do not receive high salaries.
Prepare for having less pleasant interview that you usually have with professional teams.