Before searching for a .exe file, consider the following:
Software claiming to downgrade PS4 firmware via a simple USB or PC connection is almost always a scam or malware. ps4 tool downgrade v100 exe download work
A legitimate jailbreak method for firmwares up to 11.00, but it cannot downgrade a 10.00+ system. Understanding the Search Term: PS4 Downgrade Tool v100
If you're looking to downgrade a PS4 tool (which could refer to a homebrew application, a game, or a system software) to version 1.00, here are some general points to consider: Windows PC (Windows 7 or later) PS4 console