I'm looking at the fare rules for the currently booked R fare. I wonder what these two items mean under the change rules:

CX R- FARE FAMILY GOVERNED BY IPRP 5600 I S USED

CATEGORY 19 DISCOUNTS APPLY (it's right after the line about change fees)

All my legs are originally booked in R. If I were to change the flight after the stopover (i.e. while I'm in HKG on the outbound couple of days before the HKG-AAA flight) for the new date I prefer, flight availability in EF shows plenty of availability W9 R9 E9 Y9 B9 H9 K9 M9 L9 V9 S9 N9 Q9 O9..

But looking at the currently available fares for the new date I prefer, only Y, W and J fares are available. No current R fares are available. After I fly the first leg, during my stopover in HKG (though my final destination is AAA), will they let me use the originally ticketed fare in R class with the seat availability in R, rather than asking me to buy a currently available fare? If it's the former, then that's great, I'll just have to pay the change fee. If latter, then I have some questions:

1. Can they rebook me into a Y fare? Y costs more than R. So, will they ask me to pay the fare difference? I'm not sure what they mean by higher fare - is that by cost or cabin?

2. If I fare becomes available (it's not there currently, so I don't have high hopes), then how can I ask to be rebooked into I instead of R for that segment? The R fare in my ticket sometimes books into the I class for the intra-asia segment. I wonder if there is a way to ask for the I class seat.

3. If no R class seats are available by that date, can I ask them to rebook me into a lower class (discount economy) if available, rather than paying a higher such as W?

Finally, during my arrival in HKG, where should I go to find the closest CX customer service desk for the flight change? Do they have a desk near the path that arrival passengers take, or should I go back into the ticketing entrance to do that? I don't think I'll be able to get to the transit area since I don't have an immediate connection due to stopover.

Thank you!