A bird, what?

It is sometimes so very difficult to establish if a bird is an adult or sub-adult, male or female.  It may even be moulting, i.e shedding worn feathers so that it can grow new ones.
     So what does one do?  I decide to take images of it from as many angles as possible for clues, perhaps, an expert would be able to enlighten me.  However, with this Lineated Barbet, uncertainty still reigns.  Nevertheless, just enjoy its beauty even as its plumage does not don even colouration.