Exercise 1: Adding a Real App Icon, and Why No Transparency — Possible Solution
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Steps (in Xcode):

1. Open Assets.xcassets and select the AppIcon icon set.
2. In the current, real, simplified layout, there's a single real
   1024x1024 slot for the App Store icon.
3. Drag a real, prepared 1024x1024 PNG image (fully opaque, no alpha
   channel) into that slot.
4. Build and run - the Simulator's own real Home Screen now shows the
   real custom icon instead of the default placeholder.

WHY NO TRANSPARENCY: Xcode automatically generates every OTHER real
size the system actually needs - the Home Screen icon, the smaller
Settings icon, the Spotlight search icon, notification icons - all
derived from that single real 1024x1024 source image. Every one of
those real, smaller derived icons is displayed by the system inside
its own real, standardized rounded-square mask, applied automatically
by iOS itself at render time - the developer never draws the rounded
corners directly into the source image.

If the real source image contained transparency (an alpha channel
with genuinely see-through pixels), the system's own automatic
corner-masking and icon composition process could produce a real,
visually broken result - a transparent area showing through to
whatever real background happens to sit behind the icon (the Home
Screen wallpaper, a list background in Settings, or worse, unpredictable
rendering behavior depending on context), rather than the consistent,
solid appearance every other real app icon on the system has. Apple's
own real requirement that the source icon be fully opaque exists
specifically to guarantee that consistent, predictable rendering
across every one of the many real contexts a single 1024x1024 source
image ends up being automatically resized and masked into.

ANSWER: The 1024x1024 AppIcon source image must have no transparency
because Xcode automatically generates every other real icon size from
it, and the system applies its own real corner-masking automatically
at each size - a transparent source would produce unpredictable,
visually broken results once masked and composited across the many
different real contexts (Home Screen, Settings, Spotlight, notifications)
that single source image needs to render correctly in.

WHY THIS WORKS AS AN ANSWER
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This correctly connects the real no-transparency requirement to the
specific real mechanism (automatic multi-context corner-masking from
one source image) that requirement exists to protect against.