I would ask for these questions:
– The main elements of their culture
– Values: what are they and how they include them in everyday life
– Decision-making process (how they make decisions of what process should be improved? How do they gather information for that?)
– Relationship between company and its employees
– HR working principles and ways (Agile Hr principles or a traditional, etc)
– Way of thinking: lessons learned, bets of HR team into process etc
– Terminology they use (HR team or People team, employees or team members, etc. that also say a lot :))