Each hotel has they own policy, pls check it when booking or the step 2 email, If no special comment, the policy is:
14 days before your arrival(China date), you can modify and cancel the booking without any penalty.
(If extend days, must be situation of the rooms are available)
Less than 14 days before your arrival, any change of the booking, amendment or cancellation of the booking,
hotel has the right of charging you one night payment as penalty.(The Case of Earlier checking out is included, the same as the case of amendment)
Booking of Hong Kong Hotels cannot cancel and modify, and no refund after pay.
Example, If you are supposed to stay at hotel from 15th to 18th Oct.
Case 1: 1 Oct, you cancel the booking, no penalty.
Case 2: 3 Oct, you changed the booking from 16th to 19th, or cancelled the booking, hotel may charge you one night payment.
Case 3: You are at the hotel, you stay only 15th Oct, you pay one night payment of 15th Oct, hotel would charge you the earlier check out(Modified) penalty, one night payment, that's two night payment total you will have to make for you staying.
Case 4: no more than 14 days before your arrival, you want to extend the days of the booking, no penalty, depend on the availability of the room.