PHP/JS API Query about frequency and price

I am a programmer trying to build a system based on your API. I have 2-3 questions

  1. How latest the rates are which I will get using either your Kite JS or Kite PHP API?
  2. How frequently can I refresh the rates? I mean 1-second delay or 2-second delay I can fire the script back to fetch the new rates?
  3. API comes by default with your account right? there is no other pricing involved right?