In App.Js file I’m passing "This data is coming from Parent" to Child.Js
But here I want to pass this on button through onClick not dataParentToChild={data}. Just Like Child.Js file working in onClick={handleChildToProp}
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App.Js

function App(props) {
    // Child To Parent
    const [word, setWord] = useState("");
    const handleChildToParent = (words) => setWord(words);

    // Parent To Child
    const data = "This data is coming from Parent";

    return (
        <>
            <h1>"Parent Data"</h1>
            <h2>{word}</h2>
            <Child
                // Without button Working Fine
                dataParentToChild={data}
                // With button Working Fine
                dataChildToParent={handleChildToParent}
            />
        </>
    );
}

Child.Js

const Child = (props) => {
    // Parent To Child
    const handleChildToProp = () => {
        props.dataChildToParent("This data is comming from Child");
    };

    return (
        <>
            <h1>Child Components</h1>
            <h2>{props.dataParentToChild}</h2>
            <button onClick={handleChildToProp}>Data Child To Parent</button>
        </>
    );
};

>Solution :

You need to make the button onClick update a state to trigger a re-render of dataParenToChild, like so:

function App(props) {
  // Child To Parent
  const [word, setWord] = useState('');
  const [parentToChild, setParentToChild] = useState('');
  const handleChildToParent = (words) => setWord(words);

  // Parent To Child
  const handleParentToChild = () => {
    setParentToChild('This data is coming from Parent');
  };

  return (
    <>
      <h1>"Parent Data"</h1>
      <h2>{word}</h2>
      <button onClick={handleParentToChild}>Data Parent To Child</button>
      <Child
        // Without button Working Fine
        dataParentToChild={parentToChild}
        // With button Working Fine
        dataChildToParent={handleChildToParent}
      />
    </>
  );
}

Working solution