I want to downgrade my iOS 17 to 16

You can't. Apple only allows downgrading when it's from a beta or otherwise noted.

(257994)

Downgrading your iOS has never been supported. If that was allowed, you would be installing a previous software update with more vulnerabilities and less security fixes. Furthermore, we are now on iOS 18.

adeshola289 wrote:

How can I do that

Not possible, because downgrading has never been supported.

adeshola289 wrote:

How can I do that

Why do you want to do it? Perhaps if you explain, someone can suggest an alternate method do what you want.