I need to give free shipping to the selecetd city if the order above RS.500 also the city is selected city then the free shipping will be applied.
Out of the box Magento 1.x does not offer the ability to target a specific city with a shopping cart promotion. However, depending on your target region/city you could use a postal code. For example, In the United States, La Crosse WI has 3 possible postal codes, 54601, 54602, 54603.
You could set free shipping to this area by setting the conditional rule of:
If ALL of these conditions are TRUE : Shipping Postcode is one of 54601,54602,54603 Subtotal equals or greater than 500
Then in the Actions tab set:
Free Shipping Shipment with Matching Items
Now, unfortunately this will not work if the country/city you are targeting does not have a specific postal code you can target.
You can use magento table rate for this
You can use tablerate as
price vs destination
Take a look this tutorial