Is this a possible route?

I am thinking of the following... Flying in from Amsterdam (A), staying 3 days in Guangzhou and Shenzhen (B), then going to Hong Kong by train (HK is a possible C, but is it also eligible if you go there by train?), and then entering back to Guangzhou by train (using HK as a new A) and flying back to Amsterdam. Actually my main trip is A-B-A, which is not OK, but is using Hong Kong as C for the Guangdong trip and A for a second trip should help? I only didn't see if an onward trip by train counts for an end to Trip 1 and coming into Guangdong by train from HK as the beginning of Trip 2 possible?