After you file

I’m not sure if they could or not, but I was 18 and when I started I wasn’t full time I believe until the following year, I’m not really sure. But i went through the questionnaire in 2019 and it shows me eligible for the Opportunity credit. I was working full time, & when I filed it in 2020 I was already moved out on my own in my own place. 

also, even if I worst case cannot claim the credit, can I just amend the The return anyways just to add that tax form? Is it safe to leave as is? I hear most people run into trouble if they pass 3 years.