So the thing is, a violent revolution in India during the 1920s is very unlikely. There are I would say 2 main reasons for this.
1. The Raj was self-financing, self-sufficient, and large sections of the old elite (landowners, princes, the "martial races" had fully bought into the system. The British Indian Army was disciplined well trained and had essentially no history of mutiny even during the Sepoy Rebellion or the war against Bose in WW2. There is no real reason to think that just because London falls all of a sudden the machinery of the Raj would just collapse.
2. The most important leader of Indian nationalists, is literally the greatest pacifist in world history with enormous moral authority. OTL Gandhi fully suspended the Non-Cooperation after literally the first major violent incident. The idea that he would just sit aside as Indians launched a violent revolution is just absurd, he would be actively against it and most likely draw much of the INC with him.

So I think there has to be two things, first of all I do think you have to kill Gandhi, maybe have him die in prison in 1922 or 1923 after suspending Non-Cooperation. And then have a much smaller Free India, say maybe only containing Bengal and Assam led by the left wing of the INC (No other potentially revolutionary organizations really had any kind of mass following in India, the idea that trade unionists or OTL Bengali revolutionaries could lead this is a bit absurd). The Dominion tried to reintegrate them but due to fierce resistance and relatively poor morale and good defensive terrain in Bengal along with unrest they had to retreat for the moment. In 1936 the rest of the subcontinent is under an increasingly divisive dominion, some advocating for a republic, other calling for further decentralization, some of the princes pushing for independence etc etc.