Reuse of Mapping from PI 7.1 to PI 7.3 (Single Stack ) for BPM Interfaces

Hi,

We are migrating from SAP PI 7.1 to SAP PI 7.3 (Single Stack) and we do have BPM interfaces and where we have complex mapping.

Question 1: Can we reuse the mapping when we build the NW BPM interface?

Question 2: One of the BPM interface we need to build is collecting 2 IDOC's and generating the output file. can someone help me how I can build this in PI 7.3 single stack.

Thank you,

Kishore