Running processes from 6.3 on 6.6 should mostly work, except for some subtle changes maybe. The only one that comes to my mind is handling of queue retries logic on session end, which was changed in 6.5 and reverted in 6.5.1 I think.
Importing processes from higher versions to a lower ones might work, but obviously not gauranteed - there are new features that is not supported in previous versions.
I think 6.6 also introduced some changes in xml format, you can probably find it in release notes.
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Andrey Kudinov
Project Manager
MobileTelesystems PJSC
Europe/Moscow
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