Question

Вопросы в англ можно начинать со слов "By who...? " Например, "By who a bunch of flowers was given?"

Answer 1

Нет. Who gave a bouquet of flowers? так будет правильно 

Answer 2

Нет, вопрос будет поставлен не корректно, лучше всего начинать вопрос такого типа с Who и в конце вопроса ставить by
Пример: "Who a bunch of flowers was given by?"

Answer 3

By who a bunch of flowers was given?

The question "By who a bunch of flowers was given?" is grammatically incorrect. The correct way to ask this question would be "By whom was a bunch of flowers given?" or "Who gave a bunch of flowers?"

As for the answer to the question, without any specific context or information, it is impossible to determine who gave a bunch of flowers. The identity of the person who gave the flowers would depend on the specific situation or event in question.