Identification tag for bridges above railway tracks.

Hello. I am using mapbox directions api for my routing application. I want to know is there any specific tag that could let me know about the bridges that comes above any railway track…?? Regards!!

There is no such tag. You can see that a road is on top of another “OSM way” by comparing the layer tags. But you have to use some other logic to determine a road on top of another road, a waterway or a railway. E.g. by retrieving the other OSM ways in the neighborhood of the bridge and compare their layer tags.

Is there any railway api which provides live status of train n crossings for India ?

OSM does not have that data and does not intent to collect such data. This data is typically provided by the operator of the trains and you have to start your search there.