When can u change a company when GC processing is undergoing?

Hi Saurabh,

             I just wanted to check if employer A is filed for my GC and its under process
  1. When will i be able to change my company without disturbing the GC process?

  2. Is it after I-140 or I-498?

  3. Should i stick to employer A until the entire GC processing that is usually 10 years?

  4. How long does it take for I-498 or getting an EAD usually?