How to remove two factor authentication form iPhone?

If this is a “newish” AppleID, 2FA is not optional and can’t be deactivated.

So, it’s best to fully understand it by carefully reviewing these two articles:

Two-factor authentication for Apple ID - Apple Support

Get a verification code and sign in with two-factor authentication - Apple Support

You may only turn off two-factor authentication if you signed up for it less than two weeks ago.

Two-factor authentication for Apple ID - Apple Support

If you were eligible to remove Two Factor, you received an email from Apple with a link that must be used to start the removal process.

If you did not receive an email with this information, you will not be able to remove Two Factor.