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Great. It works! Since you are knowledgeable on topic, does only 2.1.6 need manual disabling of dlc?
 
... does only 2.1.6 need manual disabling of dlc?

Used to be the case for the older versions and thus also the ones before 2.1.6, as far as i recall, but i don't know what the current state of those is.
I'm not that knowledgeable, but would recommend anyway, to simply rename the current version folder before downloading an older version.
That way you can easily make use of the now current version without download again when you don't want to play the other version anymore.

IF your question refers to the timeline of DLC releases you can check that
here
https://steamcommunity.com/sharedfiles/filedetails/?id=483507497
or here
https://ck2.paradoxwikis.com/Downloadable_content