Answering your questions:
whether all of the above are valid.
no, they are not.
process.ENV is not the same as
process.env. In fact the built-in
process does not have an
ENV property; so it is not valid unless you create a
process.ENV property (wichi is a very bad idea btw) But in windows
process.env.port they are interchangeably valid
Why are they valid ? because eventhough JS is case sensitive, the standard
process.env property is, under windows, for cross-platform compatibility.
is there a difference between any of them ?
.ENV are different totally different
.ENV does not even exist; on windows between
.PORT there is not any practical difference.
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