The Meaning of Life, the Universe, and Everything.
I have developed a utility for creating data pack tags that allow for more concise and intuitive syntax as well as greater functionality such as removing specific entries, filtering entries, and sorting entries.
To download the other ones you need to make a folder in the versions folder for minecraft and put the client and JSON file for the versions in there. They all need to be named the same aside from file extensions. Once you do that, you will be able to choose that version when making a new profile with the minecraft launcher.