You want to reverse geocode (obtain an address from latitude/longitude coordinates). You can obtain a street address directly from the LocationSensor (CurrentAddress) where this is based on your device’s present latitude and longitude. You cannot obtain address information from an arbitrary latitude / longitude pair with Blocks.
The LocationSensor provides reverse geocoding using Google’s database for free when used with a GPS receiver’s provided coordinates. Google provides that service outside of the LocationSensor when you obtain a Map developer license and use Google’s Map api to reverse geocode.
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No. Only can reverse geocode if you use the address from the lat/lon coordinates from the LocationSensor. For anything else, use Google's api or an online service. You cannot provide an arbitrary latitude/longitude and geocode.