The test on AMCAT platform consisted of 5 sections - Aptitude, Logical reasoning, Verbal ability, Technical and Coding. Each section was timed.
The first 3 sections had easy-medium level questions. The coding section had 2 questions to be solved in 60 mins.
First was a pattern printing question (Ref: https://www.geeksforgeeks.org/how-to-learn-pattern-printing-easily/ ).
The second was the standard backtracking problem of mouse and cheese (which is a variant of this problem https://www.geeksforgeeks.org/rat-in-a-maze-backtracking-2/ ).
I was able to solve most of the questions in the first 4 sections, and passed all test cases in both the coding problems.
84 students out of 400 were shortlisted for the interview round

This round started with my introduction and I was asked 4 puzzles, out of which I was able to answer the third one properly but only attempted the other 3. I wasn’t silent because I didn't know the solution before for the other 3 puzzles, but tried my best in explaining various approaches to the other 3 puzzles
The 4 puzzles are:
1) https://www.geeksforgeeks.org/puzzle-4-pay-an-employee-using-a-gold-rod-of-7-units/
2) https://medium.com/productsocial/turn-on-the-flashlight-af0568b646e2
3) https://www.geeksforgeeks.org/puzzle-3-cuts-cut-round-cake-8-equal-pieces/
4) https://www.popularmechanics.com/science/math/a24208/riddle-of-the-week-6/
Further, 41 students were selected for the HR round.

This round again started with my introduction. I was told to brief my CV in short. I told my technical skills and explained all my projects in brief.
Then I was asked why I wanted to join Citi. I explained how I liked finance and technology both, and wanted to lead a team in the company and keep up with other competing fintech companies.
Finally the interviewer asked if there were any questions for me. I asked about his experience in Citi, and the skills I needed to develop further.
After this round, 10 students were offered the internship

1) Don’t write things that you are not sure of, in your CV, as the interviewer may deep dive into that topic.
2) Try to put whatever comes to your mind in good language if you don’t know the exact solution to a problem, as they observe your thought process importantly.
3) For the HR round, prepare your introduction and common HR questions well before the interview. Mock interviews help a lot! . Actually before Citi came, I was rejected in the managerial round for Wells Fargo Internship. Then a friend of mine (Hasan) suggested that I should give a mock interview to him. I realized a lot of mistakes in my introduction and my way of answering too, because of which I was able to give my best in this HR round. (Thanks Hasan!)

Be confident and talk to the interviewer as naturally as if he/she is your friend. All the best!