What does SAP ship that makes UI-layer extension of transactional apps possible?

How do you prove the extended service really carries the new field, rather than trusting generation?

What are the six UI-layer extension steps?

After successfully generating a custom OData service in the back end, it is still inaccessible from the client. Which registration step is missing?

In an SAP Fiori extension scenario, which skills does each layer demand?

Once a custom app is deployed, which steps publish it to the launchpad?

Before extending a delivered app, where do you find its package, DDIC structures, and extension points?