Can we use Binary Cross Entropy for Multiclass Classification? In this link, the author has implemented a CNN which classifies 15 classes and has used Binary Cross Entropy as the loss function. But since it's multiclass classification, is it valid to use Binary Cross Entropy? Or should we use Categorical Cross Entropy instead?
Use categorical_crossentropy when it comes for Multiclass classification, Because multiclass have more than one exclusive targets which is restricted by the binary_cross_entrophy.

binary_cross_entrophy is used when the target vector has only two levels of class. 

In other cases when target vector has more than two levels categorical_crossentropy can be used for better model convergence.