1) Is this natural?
2) Are proved and proven both okay?
She reported him for vandalism, but it couldn't be proved/proven that it was him.
anonymous 1) Is this natural? Yes. anonymous 2) Are proved and proven both okay?
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anonymous1) Is this natural?
Yes.
anonymous2) Are proved and proven both okay?
Yes. I would use "proved" there. I tend to use "proven" for the adjective before its noun.