"Use your Always Free resources as long as you want with no time constraints—subject only to the capacity limits noted. When your 30-day trial period for the expanded set of services ends, you can continue using Always Free services with no interruption.
Always Free and Free Trial instances can be seamlessly upgraded to paid at any time. Existing Oracle Cloud customers have access to Always Free services automatically—no new sign up required."
Fact: your account will be terminated IMMEDIATELY after the trial, no reason given and no warning given.
And what the cloud support has to say:
"We see the System terminated your account and unfortunately we can't reactivate or restore the account. Thank you for chatting with us. Have a good day!"
and terminated the web chat.
Dear Oracle, please update this page to say, "always free is only for those who buy something from us within trial period." :D