JSFiddle - React, Tailwind, and code Playground

JavaScript

const str = 'ABCDEFGHIJKLMN'
    const result = str.match(/.{1,4}/g)
      .map(i => i.split('').reverse())
      .reduce((res, col) => {
        col.forEach((c, i) => res[i] += c)
        return res
      }, ['','','',''])
      .join('')
console.log(result)