My 18mth old cries inconsolably in accompanied playschool. He counts lights, rolls about, walks and identifies alphabets on the wall. Is he autistic?

Can't diagnose... It isn't possible to diagnose autism based on the amt of info that you can give in this short question format. It is a complex diagnosis & requires that you discuss concerns with your pediatrician. Does your son make eye contact? How is speech? Just two questions that would be asked AND observed. What you described doesn't worry me BUT you are there and you are worried - talk to your doctor!
Toddlers. I agree with Dr. Noonan. You are describing several different behaviors, none of which are alarming in an 18 month old and actually sound healthy and appropriate if not advanced. Talk to your pediatrician -and these behaviors are not because of vaccines. Hope this helps you.