Yes. If you want the separate high-quality soundtrack files, you must download this bin file.
Sometimes. Certain game updates may require a "checksum" of all original files; if optional files are missing, the update might fail to install. How to Use the File fg-optional-bonus-soundtracks.bin
In a typical repack, game data is split into mandatory and optional files: if optional files are missing
No. You can skip this file if you only want to play the game, as it does not contain the core game assets needed for execution. fg-optional-bonus-soundtracks.bin