Let's analyze the stress patterns of the words in each group:

1. **A.festival** (1st syllable), **B.contestant** (2nd syllable), **C.atmosphere** (1st syllable), **D.family** (1st syllable)
- The word **B. contestant** has a different stress pattern (2nd syllable) compared to the others.

2. **A.village** (1st syllable), **B.bamboo** (2nd syllable), **C.away** (2nd syllable), **D.obey** (2nd syllable)
- The word **A. village** has a different stress pattern (1st syllable) compared to the others.

3. **A.custom** (1st syllable), **B.worship** (1st syllable), **C.maintain** (2nd syllable), **D.midnight** (1st syllable)
- The word **C. maintain** has a different stress pattern (2nd syllable) compared to the others.

4. **A.holiday** (1st syllable), **B.decorate** (1st syllable), **C.offering** (1st syllable), **D.addition** (2nd syllable)
- The word **D. addition** has a different stress pattern (2nd syllable) compared to the others.

5. **A.laughter** (1st syllable), **B.prepare** (2nd syllable), **C.chopstick** (1st syllable), **D.heaven** (1st syllable)
- The word **B. prepare** has a different stress pattern (2nd syllable) compared to the others.

So, the words with different stress patterns from their respective groupings are:
1. B. contestant
2. A. village
3. C. maintain
4. D. addition
5. B. prepare