Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: IB+ Gold, TK E+, Hyatt Globalist, Marriott LTP, IHG Diamond
Posts: 14,182
In general, you might be able to change dates. (although you definitely can't book for December 2024 and then pay later to change to actually fly in 2025 or any other date that didn't fall within this promo) You also can't change from peak to.off-peak dates or vice versa.
Definitely no changes of route, origin, destination, etc. That's all cancel and rebook.