It sounds like you're asking for a review of — likely a service, tool, or seller claiming to downgrade PS4 firmware (e.g., from 9.00+ back to 6.72 or 5.05 for jailbreaking).
"Sistro" is a specialized tool for users already on 9.00 to "clean" their console or reinstall the firmware without updating to the latest version. It is a magic tool to downgrade from the latest firmware (e.g., 11.00) to 9.00. If you are on the latest firmware, you currently cannot hack or downgrade your PS4. sistrodowngradeps4
The keyword refers to the intersection of two major pillars in the PlayStation 4 modding community: the elite developer SiSTRo , creator of the essential GoldHEN homebrew enabler , and the complex process of firmware downgrading (also known as "reverting"). It sounds like you're asking for a review