By 8 o'clock yesterday he had done his homework
Общий
Had he done his homework by 8 o'clock yesterday?
Специальный
By what time had he done his homework yesterday?
К подлежащему
Who had done the homework by 8 o'clock yesterday?
Альтернативный
Had he done his homework by 8 o'clock yesterday or the day before yesterday?
Разделительный
By 8 o'clock yesterday he had done his homework, hadn't he?