Same as in English... "For each" (每个) vs "For all" (所有)

Most of times. This two is the same. Just like 每个我都喜欢。所有的我都喜欢。Means I like all of those. But I think ’所有的‘ tone of voice is stronger than '每个'。

每个 = every 所有的 = available not everyone in China can speak Mandarin => some Chinese can't speak Chinese => 有的 中国人 不 会 说 普通话。 = yǒu-de Zhōng-guó-rén bù huì shuō pǔ-tōng-huà.

Please attention to 个， this is one kind of classifier. 量词，but there always use following 每种，每根，每条，每次，每张, ect. to describe in quantity of numbers. 每种植物，每根笔，每条鱼，每次看书的时候，每张纸。Different nouns should be used different 量词。 So 所有的植物，所有的笔，所有的鱼，所有的纸，但是我们通常不说“所有看书的时候” ，因为“每”更强调个体的是数量而且有一定重复或者频率性的事件发生。"所有"强调的是全部的。

every 每个 not every 不是每个 all 所有 not all 不是所有 i think they are the same so"不是每个中国人都会说Mandarin" and "不是每个中国人都会说Mandarin" are both right