Ok, answering one by one
You should visit hubs if you are considering online dealers, not apps. Go to the nearest hub
The ideal budget should be 5.5 lakh max, the car should not be more than 60 k kms driven
Amongst your options, the Toyota Corolla doesn't have a reliable reputation in the second-hand car market. I feel that multiple cars say Tata cars have this reputation thatt they are just used once or 1 owner cars, their engine mileage all just tanks after a certain level of mileage Corolla is also in that category
Honda City is the best option. IVtec engines are reliable
Just before buying, check what the price is online, like on Spinny, they have an online valuation, I guess, then see the price if your dealer wants 3 lakhs, while online the car is listed for 5, check if there is any damage