In v2 we used features for the last couple of years that seem to be absent in v3:
1. get list of statuses for activities (returns "Resource not found" in v3)
2. get workflow status in activity notes (v3 results omit this field, and no display_column capability exists in v3 to add it back)
3. get activities per company (been using this capability since Q2 2015 in API v2, job order was part of the query string, until somebody there broke it, but they enabled a job_order_id filter that has been working since Dec-2016 and does not exist in API v3)
See Filter or query activities by job ID in the v3 forum
https://groups.google.com/forum/#!topic/cats-api-v3/fB2mMZzZBsUHopefully v2 keeps working until these features exist in v3
Thanks and regards,
Bryan