Were the first students accepted by our university in 1973? - общий вопрос - вспомогательный глагол выносим перед подлежащим.
When were the first students accepted by our university? - специальный вопрос КОГДА?
Who were the accepted by our university in 1973? - специальный вопрос КТО?
What students were accepted by our university in 1973?- специальный вопрос КАКИЕ СТУДЕНТЫ?
Why were the first students accepted by our university in 1973? - специальный вопрос ПОЧЕМУ?
By whose university were the first students accepted in 1973? - специальный вопрос ЧЬИМ УНИВЕРСИТЕТОМ? этот же вопрос в другом варианте: Whose university were the first students accepted by?