Amazon Sr Developer interview questions

Recruiter contacted me about open positions. I indicated I was interested in technical lead positions. Recruiter sent me a coding assessment. It was an online assessment with a 90-minute time limit. It contained problems on data structures and algorithms. Many language options were offered. The recruiter was very helpful and he shared several links to challenge questions with me. However, even after spending several hours answering the challenge questions, I still found it very difficult to complete. I completed the assessment a few days later. A day after this the recruiter emailed to say that they were moving forward with other candidates.

I am referred by an employee in a forum and got contacted by a recruiter later on. They invited me two do 2 on-site interview instead of phone since we are all in Beijing. I am pretty sure that the second interviewer thought I am not suitable for this position (see the questions below).