I contacted HR about a role I was interested in via email and was connected with a HR rep who scheduled a phone screening. As it turns out, the role requirements on the website and what TA wanted were vastly different. There were experience and skills TA wanted that were not listed in the role description. Phone screen lasted all of 10 minutes, I politely ended the conversation when it was clear the HR rep wasn't interested and they wanted someone with a different skill-set. I followed up with the rep to thank them for talking, despite the conversation being unproductive, and then later followed up with a question about another role which received no response. HR responsiveness and professionalism leaves quite a bit to be desired.

Lots of people will ask you very varied questions. Don't worry about meeting the CEO as while he pauses to think he is a great guy with a clear sense of the business. To get into a good role at the company you must get approved by all that interviewed you, so it's hard but if your good then while daunting it's worth it