What are the most important questions to ask a vendor when evaluating a new CRM?

In my industry I have to ask these questions. 

1.  Compatibility with our Dealer Management Software (the brain for our company)
2.  Compatibility with our website and it's widgets
3.  Compatibility with our AI tools
4.  Compatibility with our third party vendors 

If the answer is no to 2-4 then I ask if we can have a work around.  The first item is a deal breaker.

Once we get past that I ask them about how it manages the work flow, how it notifies the users for tasks etc... 

There are 2 fundamental questions I would ask regardless of CRM usage:
1. How does your TRUST layer guarantee my data’s security?
2. How is your data layer shared across your CRM applications?

Depends on the level of detail and the particular area you are focused on but here are some I suggest asking. Can you show me an end to end scenario based demonstration which includes how AI can be leveraged within your platform? What is the basis of your ROI for customers? What are you differentiators? What is your customer retention rate? What is your development roadmap and R&D investment/focus? What are your support levels/SLAs? Who are your best implementation partners? What reference can I talk to that is most like our organisation?