nothing 5 問

意思上只有(1)與(4)對。

nothing 是零是無，是不能做無事出來的，所以不能用被動語態。「無被發生了」--這太怪了。
(2)，(3)，(5)都是被動語態：主詞+(be)+過去分詞+...(~by)
(5)就更是文法錯了，因為作為動詞-ing前必須有(be)的助動詞來扣成進行式。

(1)已經可以了。(4)，past perfect 通常用以比較兩個過去了的動作發生之先後。

nothing had happened, but it is more suitable when you're referring to something that happened in the past. The most appropriate phrase, which is not listed above, is NOTHING HAS HAPPENED.

Nothing happened means that it took place at a certain time. But because your phrase is 無事發生過, which is over a certain period of time (the 過 is responsible in providing this information). If it is 無事發生, then NOTHING HAPPENED should be used.

The rest are passive voice, and ALL of them are, really, grammatically incorrect. Technically speaking, you can't 'happen' nothing, can you (as it means nothing IS/WAS HAPPENED by something/someone).

Nothing being happened is, by all means, a bag of rubbish.