I promise to not exchange your gift.
i went on a holiday but misinterpeted spoilt it
No, "holiday" should not be capitalized in this sentence. Capitalize the first word in the sentence and proper nouns, but not common nouns like "holiday."
Example sentence - The most pleasant experience on our holiday was feeding the ants at our picnic.
In another 3 days, he would be flying to Spain for a holiday.
No. It is not a sentence.
I wouldn't exchange this holiday, even for threebirthdays.
This sentence is a "conditional sentence."
i think.
The holiday resort was lovely
Example sentence - We ate at restaurants while we were on holiday.
Yes this is a correct sentence.