If you are looking to downgrade a PS4 from a modern firmware to a legacy one, here is the technical reality, the specific risks involving error codes like SU-42118-6, and why the "USB method" is widely misunderstood.

: Open the PS4 to access the motherboard. Identify your Syscon chip (it must be a chip, often marked with "A0"-C).

This process is intended for educational purposes and for repairing consoles you physically own. Downgrading a PS4 to 9.00 is often used to bypass security, which may violate Sony’s Terms of Service. If you connect a downgraded console to PSN, Sony will permanently ban your console ID and PSN account. Do not attempt this on a console you use for legitimate online gaming.

Sony designs the PS4 with a "security fuse" system (often referred to as ). When you update your console, the system permanently records that a newer version has been installed. Because of this:

Skilled hardware engineers can use a (like a Teensy++ or a specialized programmer) to physically dump the BIOS/NOR flash chip from the motherboard. By hex-editing this dump, they can theoretically change the reported firmware version.

You're looking for information on downgrading your PS4 from firmware version 13.02 to 9.00.

I had bought a "broken" PS4 off Facebook Marketplace for $40. The listing said: "Won't update. Stuck in loop." What the seller didn't tell me is that his nephew had tried to jailbreak it, botched the update, and left the poor console in a state of quantum purgatory—partially on 13.02, partially convinced it was on 9.00.