what if by mistake we click on upgrade button ? how to undo this? Is it possible to downgrade to account to free trail again?
You may contact Billing Support, but I think that the process is not reversible (unless the Support of GCP agree you help you doing that, somehow).
Although you’re no longer in free trial tier, your free credit balance remains and you can continue using it. Any expense will be deducted from this free credit balance. Only when your consumption is higher than your free credit balance, your actual credit card will be charged.
GCP has "always-free" tier services, so as long as you deploy your lab within those limits, you won’t be charged. Check out the docs here.
You may want to disable billing from your account, so that you won’t be charged either (of course you won’t be able to use your free credit balance too, if there’s anything left).
Thanks Taun for your response. Do you think I should go ahead and delete the account ? and create another fresh account ? Can I use the same credit card details while creating 2nd trial account ?
I tried to look for any official statement from Google about this matter but could not find any. But since Google asks for a valid credit card as a proof of real identity to prevent spamming and abusing of using GCP (i.e. one card correspond to one identity), that might logically mean they won’t allow the same credit card to be used for opening another free-trial of GCP. You can just left your current account as-is, and use the free credit balance for your study on GCP until it’s empty. However, you might want to set a budget alert and closely monitor it so that your CC won’t be charged without attention.
I did use same credit card/debit card on 3 GCP accounts without any issues