Hello Chris,
Thank you so much for your help.
We surely need to implement the identity verification feature to sell a Verified Certificate.
Putting that aside, I'd like to ask another question below.
I'm thinking about selling seats via payment service except for Cybersource.
To do that, I'm looking up what features have on Opend edX.
As you've already implemented, I guess,
edx.org has 2 options for enrollment.
The first one is that students can be enrolled without payment for auditing.
Another one is that students who want to get a Verified Certificate purchase seats.
That mean,
edx.org can offer 2 options on course page at the same time as I attached image.

As far as I set up configuration, cart button showed up on course information page without button for auditing.
How can I do that?
Thank you.
Harry