I want to downgrade ios 16.4.1 to ios 15

It is a bad idea to downgrade an iOS version and Apple blocked this to the ordinary user for security reasons. It’s now a one way street, you cannot make a U-turn.

Unfortunately this bad practice of holding on to old iOS versions is caused by some overzealous corporate IT admins who think that they have to approve all upgrades before they are passed to supervised corporate or BYOD handsets.

If you use your personal device as part of BYOD at work you may have encountered this when your IT admin blocks you because you are running your device on latest iOS. I am assuming this may be the reason you want to downgrade.

Apple does not support downgrading the iOS version.