Short emergency visit for three days

Gio, you mean that you will fly to HK from Guangzhou and then to Amsterdam when returning? If yes, you cannot use the 72 hour free transit because your route goes like this: HK - Guangzhou - HK and this is not a valid transit route. But if you can fly back to Amsterdam from Guangzhou directly after visiting your friend, then you are eligible for the 72 hour policy.