"no you ni" and "da"?

As for "n da", it's short for "no da". I've talked about it with a native speaker and she said sentences that end in "n da" are universal statements that declare that X always does Y and that Xs are always Y.

Like in the current Naruto closing theme: "誰だって失敗はするんだ。" "Everyone makes mistakes". By the way, is "誰だっては失敗がするんだ。" also correct?