How to downgrade an iPhone 4S on iOs 7 to iOs 5?

How to downgrade an iPhone 4S on iOs 7 to iOs 5?

Unless you saved the SHSH Blobs on iOS 5 it is impossible

Apple have to confirm the restore process, to stop people from downgrading they will not confirm anything that is not being signed, which is anything bellow iOS 9.1, so any downgrade without SHSH Blobs is impossible

Been there, TRIED THAT
Apple covered all bases - once you upgrade, provided no external back up -- you can't go back to previous versions.
This is why I haven't upgraded mine in a few years LOL (but I don't use many apps)

You don't. Plus nothing would run on it, iOS 5 is a long time ago and no apps run on that. Many good things have been added since then, I can't imagine why you would want to go back.