Fringe, SPOILER ALERT

OK, so we know that Bell is still really devious and unethical. Super devious and unethical, in fact. But my question remains: which Belli are we seeing? Are we seeing Walter's friend Belli, from our world? Or are we seeing the Alt-Bell? Which one is Nina Sharp communicating with? Which one did Olivia see? Which one did the surgery on Walter? It seems to me that the answers to these questions change the whole picture of what is, exactly, going on here.