What funding to include in an old paper?
As I often try to remember, a stable baseline for such things is honesty. So, perhaps something like &quot;the main part of this work was partially funded by X. Revisions were partially funded by Y and Z&quot;.
(I'm assuming that &quot;partially&quot; is the correct thing in your situation...)
In the U.S., in math, the funding agencies not only &quot;require&quot; such acknowledgements, but do want to be able to &quot;point to&quot; them to make an impact on higher-ups, including the U.S. Congress. I somehow doubt that Congressional staffers are fact-checking the NSF's claims... but, still. :)
Similarly regarding affiliations, I think, though in that regard the more functionally relevant item is probably &quot;current contact information&quot;. At the same time, you could also credit former employers/institutions with &quot;partially funding&quot; the research. Although I don't see this in any U.S. math rule-book, it would certainly be honest and fair.
(Years ago, a senior colleague of mine here in Minnesota, Steven Gaal, in the intro to his very nice monograph on linear analysis, explicitly thanked &quot;the farmers and workers of Minnesota&quot; for supporting him while he did that work.)