How do I disable 2FA on an iPhone after mistakenly enabling it?

If you have ever recently created a new Apple Account, you would see the 2FA is required and you have no option to have an account now without 2FA. It is only on older account where there was still an option to turn it on and also the ability to turn it off within the 2 week period using the email. Check your Junk Mail or Recently Deleted emails to see if you can find that email the day you turned it on. Many services and features now are not available without using 2FA.

As for using 2FA, Chattanoogan is correct that it is only required the first time you sign in on another device, where then that device becomes a Trusted Device after entering the verification code and you should not be required to enter it again. If you are seeing that on a work computer, it may be that it is being managed by an employer or using a VPN that clears each session so that device cannot be remembered. I haven't had to enter a 2FA code for my Apple Account on my Mac, since the one time I purchased it 5 years ago. Also when I set up Apple TV on my LG TV, I was required to enter the 2FA code, but that was again only once and has not happened since.

No there is not a reset that will drop the 2FA. It is activated on the Apple Account, so resetting a device has no effect.

Manage two-factor authentication for your Apple ID from iPod touch - Apple Support

"After you turn on two-factor authentication, you have a two-week period during which you can turn it off. After that period, you can’t turn off two-factor authentication."

Completely understand your misgivings, but ….

… your concerns are a bit unfounded.

Your 2nd factor is needed ONLY the first time you log in with a new Apple Device.

Once you’ve done that, the device becomes a “Trusted Device” and doesn’t need to be re-authenticated with 2FA.

Restated, you might never do it again until you purchase a new Apple device.

Suggest that you thoroughly familiarize yourself with the following (especially the section on setting-up multiple additional Trusted Numbers)

Two-factor authentication for Apple Account - Apple Support

About trusted phone numbers and trusted devices for Apple Account - Apple Support

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

Sounds like you computer isn’t saving your Apple Account info within your Mac’s “user account”

That would indeed cause numerous usability problems.

You Apple Account info should be configured in “Settings.”

See details here:

Apple Account on Mac - Apple Support

It’s my own personal computer. My account is ages old and not one of these newer accounts. When I’m on my computer it will repeatedly ask for the code being sent to the phone when I access iCloud.com. How do I make the computer trusted and is it one of those things that when I clean the cache and history of browser that will be deleted?

It’s does repeatedly ask for a code on my computer that’s a personal computer and not managed by another like employee computers are.

I don’t know why but that’s the behavior. I pulled up a browser to use iCloud.com and logged out afterward. Later I repeated the same action and another code was sent to my phone. If there is a way to keep the trusted set on then I’ve not found it.