Good luck trying to fit in a GOU in that budget in todays world. :(
But yeah if market was normal, I would have gone for i5-11400F + 1650 Super in this range
A lot of laptops are due to launch in coming months with Ryzen + RTX 3000 Series in India.
You might want to wait for a month or two at least! Most of them started shipping in USA earlier this month.
You can just take the RAM with your Laptop and get it installed at the Service Centre for free if your Laptop is still under warranty.
Shouldn't be any problem!
Yes, you're always better off with good airflow to combat the testing summers of India tbh
Consider Lian Li Lancool II Mesh as well... can't go better at this price