So you learned nothing and refused to accept criticism as anything other than a personal attack on your character. Not even gonna address your continued crappy defense of your crappy take.
Also, your mother was a hamster and your father smelt of elderberries. There’s your insult.
You can create endless Gmail accounts for free and google has several different 2fa options to choose from. So you could make one ‘[email protected]’ or have each person on their own device create dummy Gmail addresses like ‘[email protected]’ and have each student go through the process individually. They would only be temporary in that you’d just stop using it after the class and google would eventually get rid of it(maybe?) After long enough without any use. I don’t think you’re going to find something that just generates dummy 2fa codes for demo purposes.
Is this being taught in a computer lab or will the students all have laptops or smartphones? If so I would almost be tempted to just walk them through all creating a temporary email address and then setting up 2fa on the accounts. But yeah Gmail accounts.