i want to disable two factor authentication feature to able to use legacy iphone, ipad products without any hassle, what can i do?

If 2 factor authentication has been on for more than 14 days, then it cannot be turned off, however, 2 Factor Authentication is tied to your Apple ID not your devices directly, it has no bearing on any physical product you may want to use with your iPhone or iPad.

What exactly are you trying to do, what do you mean by "legacy products"?

2 factor authentication should be transparent in every day use of the device. It should only come up when trying to sign in to an iOS device for the first time, or logging into iCloud through a browser that has not been used before.

It will not stop you from using any apps, or physical devices with the iPad or iPhone in any way.

It has no effect on any other things you may do with the iPhone.

If you are worried about older devices, they can still use two-factor.

They won’t prompt for the authentication code, but you can just enter it after the password.

See this article: https://support.apple.com/en-us/HT204915 (one of the last paragraphs covers older devices).

Again, 2 Factor authentication is tied to your Apple ID, it has nothing to do with your phone #.

You cannot reset your phone #. That is defined by your carrier. Thy provide the number, only they can reset it.

The only time you should be asked for the code is if you are logging in to iCloud. You can choose to trust the browser you are signing in with if you don't want to be asked for the code every time when using that browser.

See here: Two-factor authentication for Apple ID - Apple Support

When you sign in on the web, you can choose to trust your browser, so

you won’t be asked for a verification code the next time you sign in

from that computer.

You can't turn off 2 Factor Authentication for only one device. 2 Factor Authentication is tied to your ID, not the device(s).

I'm not sure I understand your question, but 2 Factor Authentication is tried to your Apple ID, not your phone number.

As Phil posted earlier.

If 2 factor authentication has been on for more than 14 days, then it cannot be turned off,