Can we use Binary Cross Entropy for Multiclass Classification?
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.