The "PS4 Tool Downgrade v1.00.exe" is a tool that has been circulating online, claiming to allow users to downgrade their PS4's firmware. However, I must emphasize that:
If you have a PS4 on a vulnerable firmware (9.00 or lower), you can: ps4 tool downgrade v100 exe link download
True firmware downgrading (reverting to a lower system version) is not achieved through a "magic" file. Instead, it relies on a process called Firmware Reversion Dual Slots The "PS4 Tool Downgrade v1
Never run unsigned .exe files from unknown sources claiming to “downgrade” your PS4 — they could: ps4 tool downgrade v100 exe link download