Most of what you mention is actually a problem solving itself. One of the cause of man made climate change is overpopulation, with most of the human population being crammed into megacities of which many are coastal it means the overpopulation will probably fix itself with people living in big cities mass dying. Big and not that big cities do not produce enough food and water for themselves, density of population means they will be hotspots for contagious diseases, means of transportation out of those cities do not allow for mass migration, all these and more means those people are likely to die.

On the other hand people living in the countryside, are able to grow food, have knowledge of local plants and generally can sustain themselves have much better chance to survive the catastrophic events to come.

Though some experts think a war over water between India and China is possible, other think the collapse will happen so fast that it will wipe all possibility of military action and leave only people that will have no choice but work together to survive. This scenario is also likely.

It's been a while since I've been in India but imho this is one the places on earth with potential to survive climate change.