Also RenPy 7.4.3 is an official version, it's what the Nightly's have been on for almost a month.
No, the latest official version is 7.4.2. When talking about a software, "official" do not mean "made by the original author/team", but "released to the public".
The Nightly's is
always an alpha version. It correspond to the "devel" branch of the project, and is where everything is tested ; with "everything" including feature/code that will never made it to the release. Anyone can download it, if he want to help on the project, whatever by improving the code or just testing it, but it's not a version to be used for something else that pure testing.
Therefore, it's not an official version, nor for the public, and even less to be used in production.