[Scenario] What should be the right way to reverse this po?
the information, like previous comments, is rather high level, which entails various scenarios. I guess your question is mainly about how to bring back items posted as consumed in a production order. There are basically 2 scenarios
1 if the item has been posted as consumed by the production order hasn't been marked as finished. Then you could post negative consumption to bring those back into inventory.
2 if the production order is marked as finished, which means all posting on the inventory and financial side has been finalized. You won't be able to use the method in the first scenarios. You could use item journal to do positive adjustment to bring back items as needed.