Challenge 3: The Risk of Retouching Directly on the Original Layer — Solution Walkthrough

Why this is a real risk:

Retouching directly on the original photo layer permanently alters
that layer's own pixel data — a mistake, an over-aggressive clone, or
a healing operation gone wrong is baked directly into the only copy
of the image that exists, with no separate, untouched version left to
fall back on if the retouching turns out to need correcting or
redoing later.

The standard habit that avoids it:

Per this chapter's own material, duplicate the photo layer first (or
work on a new empty layer with "Sample: All Layers" enabled) and
perform all retouching there instead, keeping the original layer
completely untouched underneath as a safety net.

Connecting back to earlier material:

This is a direct application of Chapter 4's own non-destructive
layering philosophy, applied specifically to retouching — Chapter 4
established that keeping content on separate, independently editable
layers (rather than merging everything permanently) is the foundation
of safe raster editing generally; this chapter simply applies that
same principle to the specific case of clone/heal retouching, rather
than introducing a new concept from scratch.

WHY THIS WORKS AS AN ANSWER
------------------------------
This exercise checks that the duplicate-layer safety habit is
understood as a direct, specific application of Chapter 4's own
general non-destructive layering principle, rather than an unrelated
new rule specific to retouching alone.