As in, when listing adjectives, for example a 愉快, 安全, and 环保 summer vacation, do you say 愉快, 安全, 和 环保 的 暑假 do you need the he at the end of the list? Is this how you would list adjectives in the first place?
You can use it but it is not necessary.
Unlike English grammar, its elusive Chinese counterpart does not have a rule of prefixing conjunction to the last element of a string of parallel elements. In fact, Chinese tend to utter a really long string of nouns or phrases without using any conjunction, like 我曾经去过英国、法国、德国、意大利、比利时。
But it is now accepted by Chinese people to use the conjunction in an anglicized way, like 我曾经去过英国、法国、德国、意大利和比利时. However, some language purists disprove this usage. My college professor of EN to CN translation concurred with these views and explicitly demanded that we drop 和 when translating.
Yes, you can. Also, like English, you have option not to use 和. It depends the syllabus rhythm that you like to present to audience.
You can replace it with 及 or 與.
Yes you can. It's necessary if you only have two items (安全和愉快的暑假). The conjunction is likely to be 和, but can also be other conjunctions based on meaning.
For more than 3 items, the conjunction is not necessary, but in formal situations people tend to use it.