Weight updates in rnn

[koulritesh98]

In Chapter 12, why are we giving a previous layer delta to embedded layer embed_idx = sent[layer_idx]

embed[embed_idx] -= layers[layer_idx]['hidden_delta'] * alpha / float(len(sent))

shouldn't it be

embed[embed_idx] -= layer['hidden_delta'] * alpha / float(len(sent))

Also what is the need of updating embeddings of last word in the sentence which is being predicted by the network ?