Here are the errors identified in the sentences provided:

1. **Error**: "might be very excited if her father allowed her to take a holiday in Japan."
**Correction**: No grammatical error; this sentence is correct.

2. **Error**: "the most interesting its architecture and stories can be."
**Correction**: It should be "the more interesting its architecture and stories can be." The comparative form "more" is appropriate here, as it compares the degree of interest related to the age of the district.

3. **Error**: "We aren't certain who contacting about setting up a handicraft stall at the community fair."
**Correction**: It should be "who we are contacting about." The sentence is missing the subject pronoun "we."

4. **Error**: "she ran away yarn and had to stop."
**Correction**: It should be "she ran out of yarn." This clarifies that she no longer has enough yarn to continue knitting.

5. **Error**: "you can follow the rules and not play games."
**Correction**: No grammatical error; this sentence is correct.

In summary, the corrected sentences are:

1. No correction needed.
2. "The older a city's historical district is, the more interesting its architecture and stories can be."
3. "We aren't certain who we are contacting about setting up a handicraft stall at the community fair."
4. "My sister was knitting a scarf, but she ran out of yarn and had to stop."
5. No correction needed.