Training Encoder-Decoder using Decoder Outputs
I would like to know if it's possible to train a decoder by feeding
  its predictions at time, t-1, into the input at time-step t.


Yes, it is possible to do it. 

But I don't see why you would do it.

Υou will have accumulated error propagated and amplified in every new prediction, making your prediction to diverge from the ground truth sooner or later.