1- I have no idea about the dates, but did bSDD ever contained IFC 4 before IFC 4.3 ?
That would not make sense for me because then it would still be available (from the managing content, uri stays even when newer versions are published)
2- I know that it is not bSDD that publishes the dictionnary and it should be BuildingSMART internationnal.
If the purpose of the bSDD is to allow BIM software to request API from bSDD and some of these softwares supports previous versions of IFC then it would make sense for me that BuildingSMART internationnal also provide these versions.
I guess the question have already been raised, I just can’t find the answer why.
No, we started with IFC4.3 and plan to add previous versions, namely 2x3 and 4, when we get the resources to do it. This requires some work, as we are not uploading IFC as is, but first filter only subset of it, trim the definitions, add improved names, and integrate with the translation project (IFC is being translated into 25 languages). IFC4x3 was easier, because we already took the effort of making it more manageable with XML on github, which is not the case for older versions.