How to downgrade iphone 4s ios 9.0.2 to ios 8.4 ?

I don’t think its possible but you can try factory reset you iphone, also do backup before doing this. :) As a smart Phone user, Also install Leo Privacy Guard. It will help you to hide and secure your personal data such as images and videos. It can also lock applications.

No way in hell that Apple will let you do that.

Downgrading is becoming a thing of the past. The last device that's possible to downgrade with SHSH Blobs is the iPhone 4 and I believe the iPad 2(I might be wrong) and the iPod touch 4.

I don't think you can downgrade something.

Can't.

cant