Challenge 1: Exporting at 1080p From a 4K Timeline — Solution Walkthrough

Why this is possible without re-editing:

Per this chapter's own material, project settings (the resolution the
timeline itself uses while editing) and render settings (what
actually gets exported, configured on the Deliver page) are two
separate, independently configurable things. The timeline can stay at
its original 4K project resolution the entire time it was edited,
while the render settings on the Deliver page are simply set to
export at 1080p instead, without touching the timeline's own
resolution or any of the actual edits made to it.

Why re-editing isn't needed:

Since render settings are configured independently on the Deliver
page and applied only at the moment of export, changing the delivered
resolution is purely a render-setting change — it doesn't require
undoing or redoing any cuts, color grading, or other edits already
made at the original 4K project resolution.

What this looks like practically:

The editor simply opens the Deliver page, selects (or manually
configures) a render preset outputting at 1080p, and starts the
render — the original 4K timeline and all its edits remain completely
untouched and available if a different delivery resolution is ever
needed again later.

WHY THIS WORKS AS AN ANSWER
------------------------------
This exercise is a direct, practical application of this chapter's own
project-settings-vs-render-settings distinction to a concrete,
realistic delivery requirement.