Welcome to the forum!

1) I do not understand why you extract parts.

Why do you not use linked parts instead? (as most Finale users do)

2) You tell that the changes are not in the extracted parts.

* Are the changes in the linked parts?

Sydney,

What type of changes did you make to the score that aren't in the extracted parts?

You can use either linked parts or extracted parts. Finale offers both options, the choice is yours. As Peter said, most users use linked parts, but if you prefer extracted, that's fine too.