Can some one break these questions down and the difference please...?

Question:

-Sumimasen,
kore chigau n desu kedo.
Also what is the ".....n desu kedo"?

-Kore chuumon shinakatta
n desu kedo.

-Kore chigau to omou n desu kedo.

Answer:

-Sumimasen, = Sorry or excuse me
kore chigau n desu kedo.= Kore (this) chigau(different), n (shortened from chigau no) desu kedo(be)
More formal way of saying it would be "Koreha chigauno desukedo".
altogether meaning "This (food) is different (from what I ordered).

Also what is the ".....n desu kedo"?
"n" is frequently used in our casual daily conversation, "Anohito sitte "n" no?" = "Anohito sitteiru no?"
(You know him?)
-Kore(This) chuumon(order) shinakatta n (did not)
desu kedo.(polite way to complete sentence)

-Kore chigau to omou n desu kedo
chigau (different) to omou n (think 'so')
meaning I think this is different from (the one I asked).