How to modify the controls of React Player while playing the mp4 file. I want the option of getting downloaded be disabled

You can add controlsList="nodownload" to the video element and the download button will disappear in Chrome.

Keep in mind that people can still download the video if they really want to. An additional precaution would be to disable right-clicking on the video element:

<ReactPlayer
  // Disable download button
  config={{ file: { attributes: { controlsList: 'nodownload' } } }}

  // Disable right click
  onContextMenu={e => e.preventDefault()}

  // Your props
  url="https://media.w3.org/2010/05/sintel/trailer_hd.mp4"
  className="react-player"
  controls
  width="100%"
  height="100%"
/>