I have a question regarding the fare conditions of the ticket after a Bookable Upgrade is confirmed. Point #26 of the T&C says this: "Any rebooking or change of date will be governed by the terms and conditions of the original class ticket."

My understanding of this would mean the below scenario; can someone please confirm that my understanding is correct:

I have a Bookable Upgrade expiring 30 Nov 2025. It is highly unlikely I will make any flights prior to this date. Therefore, I plan to book a fully flexible economy class ticket for Jan 2026, say for example, to Shanghai. Of course, this would be under a fare code which allows me to use the Bookable Upgrade. Once confirmed (and if no PEY on my booked flights), I would be booked in Business Class under fare code I.

1.) If I make any flight changes, I would still be able to do so without any change fee (of course, I may have to pay any fare difference), correct? My ticket, although in fare code I, would still follow the fare rules of the original economy class flex ticket? It would not follow the fare conditions (whatever they may be) of the fare code I ticket?
2.) If I make any flight changes WHICH REQUIRES A RE-ISSUE OF TICKET, it is my understanding that I would lose the Bookable Upgrade, since any reticketing would not allow me to re-apply an already-expired upgrade cert. Is this correct?
3.) Of course, I know that I I cancel the flights, then the Bookable Upgrade cert would not fall back into my account, since it would have expired.

If anyone has any experience of the above, please share. Thank you.