we can perform the supervised classification on Sentinel 1 GRD data. But, it is not possible to visually identify the training data from the image. I have the training data in the form of shapefile. There is a way to import training data in SNAP and then classify the sentinel data.

Thank you, Sir!

Yes, of course. Basically any type of classifier will yield some result. But the results mainly depends on the training data, pre-processing methods and type of classifier etc.,