Hi,
But given the fact that things in the XML structure changed quite often between minor versions
Which xml structures were changed?

krpano should be very backward compatible.
There is no old version archive because of license reasons - there are unfortunately many illegal krpano license usages (and even more illegal Panotour Pro usages), e.g. because of licenses bought with stolen creditcards, chargebacks, cancellations, hacked Panotour versions and so on. And each new krpano version always also contains things to avoid/block the usage of such licenses.
Without these illegal usages I would be happy to offer all krpano versions from 1.0 and up of course.
The alternative would be a online-activation system, where I'm not a fan of.
Best regards,
Klaus