I have Lufthansa's flight, on web site I see that it will be in Airbus A321. In this aircraft there are very nice seats near emergency exit where there is no row in front.
One disadvantage is that for booking this seats I need to pay 25€ for each flight segment :)
If I pay and tomorrow they change A321 to A320 or A319 can I ask Lufthansa to cancel seat reservation with extra space and give me back my money?
Yes (emphasis mine):
Lufthansa says:
Operationally necessary seat changes
If Lufthansa has to change your seat reservation, for example because of a last-minute change to the aircraft type deployed, Lufthansa will do its best to reserve a new, equivalent seat for you automatically. In these cases priority is firstly given to passengers who are travelling together, such as families, so that they can still sit next to each other. After that, there is the allocation of seats with more legroom in the emergency exit rows and of aisle, window and middle seats. If it is not possible to allocate you a new seat equivalent to your original, then you are entitled to a refund of the amount you paid for your seat reservation. Please contact the Lufthansa Service Center to arrange this. Where seat changes have to be made for operationally necessary reasons, you unfortunately have no legal right to a certain seat, only to the category, such as an aisle or window seat.
