Grey area. Most anarchy servers (like 2b2t) consider gamma boosting a standard trick. However, combining Fullbright with X-Ray is universally despised. Fullbright alone gives you visibility, but not wall hacks.
Ensure the downloaded file ends with .zip . Do not unzip it. Minecraft reads compressed folders natively. fullbright 1.12.2 resource pack
A text editor (Notepad works) and any image editor (even MS Paint). Grey area