Multi-city for 144-hours visa-free

Let us see by checking one by one itinerary:

a. This itinerary could function only if you fly from Hong Kong to Guangzhou. When entering Guangdong province where Guangzhou is located, in order to be eligible for 144 hour visa free transit, the only eligible way is to fly. So, if you take a flight from Hong Kong to Guangzhou, this itinerary would be eligible.
b. This itinerary needs a ferry instead of train. Train is never eligible because it is a high speed train that has somewhat specific immigration details that cannot function with 144 hour visa free transit. So, you can take a ferry from several ports in Guangdong province, including Pazhou located almost in the center of Guangzhou to Hong Kong. However, you are informed that you will have to buy your ferry ticket in advance through Chu Kong Passenger Transport Company and to print out that ticket and to have it with you at hand. Also, you will have to take exactly that ferry you have bought your ticket for.
c. It would be eligible, but look for explanation under your itinerary "a"

The procedure is easy. If you have eligible itinerary you will just declare at the check-in in at the airport that is immediate point before your entry to mainland China that you intend to fly to the point immediate after your mainland China destination, via Guangzhou by using 144 hour visa free transit. You will repeat this when you land in Guangzhou at 144 hour visa free transit counter.