這真的是一個很好的問題.
這兩個在例句中都是介詞用法.后者比前者多了個out.
through是一個動態(tài)介詞,常與表示動態(tài)的位移動詞或（名詞）連用,如：walk through the forest.
在時間的數(shù)軸上,through表示從一段時間的起點至終點的這個過程.
多了個out的介詞throughout ,重點在這個out上.
用漢語來翻譯思考,all through the year 和 throughout the year 相當于全年和一年到頭的區(qū)別吧.
感覺最后一個例句中的have不是位移動詞,所以不能用though,
第三個例句,可以用through代替throughout,只是語氣不同.
前兩個例句不宜用throughout
這是我個人的判斷.
最好還是去查一查詞典,找出更多的例句.
《牛津雙解》
throughout
2 during the whole duration of (sth)
在（某事）的整個期間
Food was scarce throughout the war.
在戰(zhàn)爭期間食物匱乏.
Throughout his life he had always kept bees.他有生之年一直養(yǎng)蜂.
Throughout their marriage he had only once seen her cry.在他們婚後的日子里,他只看到她哭過一次.
through
2 from the beginning to the end of (sth) 從（某事）的開始至結(jié)束; 自始至終;
從頭到尾
He will not live through the night,ie He will die before morning.他活不過今天夜里了.
The children are too young to sit through a long concert.這些孩子太小,
音樂會時間長他們就坐不住了.
She nursed me through my long illness.我病了很長時間,她都一直護理著我.
I'm half-way through (reading) his second novel.他寫的第二本小說我正看了一半兒.