Connection options between S/4HANA and SAP Process Orchestration middleware

Hi experts, I would like to understand the connection options between S/4HANA and SAP PO middleware for the following scenario:

S/4HANA is SAP Public cloud-based, whereas SAP PO is in a private cloud.

1. Can a t-RFC connection be opened in order for IDoc (XML-IDoc) payloads to be carried from/to S/4HANA to/from SAP PO?  Let's say that appropriate t-RFC port connection can be opened in the private cloud where SAP PO resides; but I don't know if S/4HANA system works with t-RFC at all, and if yes, does a SAP public cloud-based S/4HANA allow that traffic?

2. Can S/4HANA system provide as well as consume a web service call with the IDoc payload?  Does the WS call have to be formal WSDL-based, or can it be a ReST-based WS?

Thanks for your inputs and helpful links!