Please advise can I apply for the VOA when I arrive at Xiamen Port and Shanghai Port ?

Peter, would you be so kind and present your itinerary, bur very precisely. The reason is very simple. Your eligibility for VOA or visa free transit depends on your itinerary. Please, present your ports of call in precise chronological order. I assume that you will have some other port of call between Xiamen and Shanghai, probably in Taiwan, because this is usual way how do cruise companies arrange their itineraries when they introduce mainland Chinese ports of call within the entire cruise.