As along as the necessary part doesn't appear at the same time, it won't function as an eye..
As along one of many necessary parts don't appear at the same time, at the current condition, it won't function as an eye.
ご質問ありがとうございます。
この場合は、「必要な部品が同時に出現しない限り眼として機能しない」は英語で「As along as the necessary part doesn't appear at the same time, it won't function as an eye.」と言えます。
また、「眼は必要な多くの部品が今の状態で同時に出現しない限り眼として機能しない」の場合、「As along one of many necessary parts don't appear at the same time, at the current condition, it won't function as an eye.」になります。
ご参考になれば幸いです。
アメリカ合衆国 
