介词OF和FROM的区别和用法?

Sametimes they are interchangable (same).
Sometimes they are not interchangable (different).
Let's see several examples.
interchangable (same):
You can choose one of them to be your asistant.
You can choose one from them to be your asistant.
not interchangable (different):
You can choose one of my guitars for your performance.
You can choose one guitar from my collection for your performance.
You can say:
"The girl from a countryside...".
But you cannot say:
"The girl of a countryside...".
You can say:
"The Great Wall is the proud of Chinese".
But you cannot say:
"The Great Wall is the proud from Chinese".