Here are some of the best channels for videos about IIT:
Pradeep Kshetrapal’s channel is very helpful.
Physics Galaxy: In case, you can’t find something on Pradeep sir’s channel, you can refer to Physics Galaxy
Mohit Sir’s Channel: Mohit Tyagi: Sir Mohit Tyagi is the best for maths. But since he hasn’t uploaded one or two chapters yet, you can refer to Pradeep Kshetrapal’s channel as he has started uploading Maths and chemistry as well.
For Chemistry: Sadly, there wasn’t any good channel for chemistry before, but I found two channels, which are very good.
Gabbar Singh Tutorials: The channel helps you focus on the concepts of the subjects.
Pradeep Kshetrapal: As I mentioned above, this cannel has uploaded videos for Maths and chemistry as well. The channel has good tutors.
Note: When studying online, you must have a lot of self-control. Avoid opening social media sites, until and unless you have completed your studies.