First of all Deeksha, Welcome to TAI
When it comes to car with CNG I would suggest you to try the Maruti Wagon R.
When it comes to automatic hatchback it would be Hyundai I10 auto and Maruti A-Star.
When you try automatic hatchbacks in India you are moving to petrol as automatic hatches are available in only petrol variants. Then I would advice you to check the Honda Brio also before making your final choice. Even though its manual transmittion its a good city car.
Test drive all the above listed cars before making your final choice.
When it comes to diesel sedan under 8 lakhs check out the all new Swift Dzire, Toyota Etios diesel, Ford Fiesta Classic and when its MUV its Maruti Ertiga.