I tried TOUGHEST JEE Rotational Physics Question from 2016

Here is my solution of the classic 2016 Rotational Mechanics JEE Advanced Question for the entrance exams to the IIT in India. Probably the toughest question to appear on the JEE Advanced. This is India's hardest exams and probably one of the hardest in the world.
Please find the original question here: https://jeeadv.ac.in/past_qps/2016_2.pdf (Q7 from this paper)
Also note that these are not official solutions and if you spot a mistake, please leave a comment.
This is an excellent question on Rotational Mechanics, involving angular momentum, moment of inertia, angular speed and more obscure concepts such as spin and orbital angular momentum.
It is exceptionally hard and hence excellent revision for JEE Aspirants looking for extra practice.
I hope this video is useful!
This video is excellent preparation for physics olympiads, JEE Advanced, JEE Main, and even excellent practice for university courses in engineering and physics.
Chapters:
00:00 The Question
00:32 Part A
02:38 Part A Alternative
03:50 B - HARD!
10:45 Part C
12:37 Part D
16:48 My thoughts on this question