Despite all the highly visible technological developments in theatrical and home delivery of the moving image that have occurred over the decades since then, no single innovation has come close to being regarded as a similar kind of watershed.

(1)that是什么用法？是image的定语从句的关系代词还是对应前面的all？

【答】that是关系代词，其先行词是developments，不是image。这从谓语动词have occurred即看出来。all作developments的定语。

(2) home delivery如何翻译？后半句 “no single innovation has come close to being regarded as a similar kind of watershed” 是什么意思？怎么理解？

【答】不能单独挑出home delivery这个词语，应该是一个整体词组：theatrical and home delivery of the moving image。其中，theatrical and home并列形容词修饰delivery，意为“剧场与家庭之间的传送”， of the moving image也是作定语修饰delivery。

【翻译】no single innovation has come close to being regarded as a similar kind of watershed：没有一项革新近乎被视为与此相似的分水岭。