You’ll need to cancel (incur fee) and rebook (assuming availability). They won’t make accommodations (no fee / availability) due to the equipment change.

I prefer EK F on the 380 over the 777 (non-Game Changer) due to the cabin noise (less) and greater spaciousness of the suite. The bathrooms (forget shower aspect for a second) are also much better. Never had service issues even when full. But at this level, it’s splitting hairs. I’ll take any EK F on the most convenient route. And I would not build in a stop in a place I don’t need to be and fly the next day to my real destination just to experience Game Changer F over regular EK F. You’re adding another flight experience in some terrible euro business / economy short haul situation — to me, it defeats the whole purpose of flying F.