Coinbase sent me a one time code to use to login after my having been locked out, but I don't know if I will ever be asked for any other code. To clearify, each time I went to login on a different device they sent me a code to use during the login process.
Where do you receive the code? To your number? Then nothing else is required. That's the code I think. And in some cases, if the device used to log in your account is known to coinbase, they may not ask for code.
Yes, they sent it to my phone, and then during the login process they sent an email to which I had to respond on the same device that I was using to try to login.
But, you now have me worried about BlockFi. If I am asked for an Authenticator code to withdraw funds it will fail. I wonder if there is any other way to test this without actually trying to withdraw funds.