yes, renaming of CACHE.DAT to IRIS.DAT is supported, but not for the system manager databases.

Either just copy your own databases that way and recreate the required configuration (e.g. security), or - if you have a lot of config -, you can install Cache (into same directory path on new server), copy manager db (and cache.cpf) across and then do in-place upgrade to IRIS.

I think Kev is right: the upgrade froze all query plans. In your DEV environment the class definition might have moved on, probably added a new field - which should cause the plan to become unfrozen but there was (is?) a bug in Caché with that. The fix is

DPV5125 - SQL: Correct frozen plan error condition of SELECT * validation

We had a patch for that for v2017.1 and it is supposed to be included in 2017.2.2, although I'm not too sure as we recently upgraded to that version and had the same problem afterwards.