For the uninitiated: You don’t choose to downgrade a PS4 from firmware 13.02 to 9.00. The universe forces you into it.
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.
For two weeks, I tried the normal routes: ps4 downgrade 1302 to 900
The console was telling me: "I see you are trying to install 9.00, but I have tasted 13.02. I will not go back. I am better than this."
If you genuinely have a console stating firmware "1302" (or similar obscure numbers): For the uninitiated: You don’t choose to downgrade
Sony designed the PS4 with a one-way street for firmware. Inside the console’s Southbridge chip (or Syscon on later models), there is a set of one-time programmable fuses. Every time you update your firmware (e.g., from 9.00 to 10.00 to 11.00 to 13.02), a fuse is physically blown.
When the PS4 boots, it checks the current firmware version against the state of these fuses. The console was telling me: "I see you
Error 900 (full code: SU-42118-9) literally means: "The update data you are trying to install is older than the minimum required version stored in hardware." Your PS4 is telling you, in no uncertain terms, that you cannot go back.
Error 1302 (full code: SU-42130-2) generally means: "The update file is corrupted, incomplete, or not meant for this region/model." However, in the context of downgrading, it often appears when you try to trick the PS4 into accepting a lower firmware via a modified USB drive or a recovery (PUP) file from the wrong region.
So when you search for "downgrade 1302 to 900," you are actually searching for a mythical process: Take a PS4 that is rejecting a file (1302) and force it into a state where it recognizes an older file (900), then install that older file. In retail consoles, this path does not exist.