Development is the change a story asks you to copy. A new costume is not a character. A speech is not a character. If the person at the end can live differently, and the story is honest about what it cost, something developed. Bandura's old finding sits under this: people copy what they see rewarded.
Three changes
A person grows, holds, or falls. Pick one. The titles are already measured.
The person at the end can do something the person at the start could not. Keep a promise. Tell a truth. Leave a house that asked them to lie. The change is the story. If you can name it in one sentence, it happened.