Can clearInterval() be called inside setInterval()?

Yes you can. You can even test it:

var i = 0;
var timer = setInterval(function() {
  console.log(++i);
  if (i === 5) clearInterval(timer);
  console.log('post-interval'); //this will still run after clearing
}, 200);

In this example, this timer clears when i reaches 5.