Kojichan

I've tried downloading the file "ysbin.rar" and WinRAR is telling me that the file is damaged.

The engine is called "Artemis", and it's a really common modern engine that's easily portable between PC, Mac, Android, and iOS. A lot of Playstation Vita games make use of it, too. It's based off of LUA scripting and XML scenes.

It depends on which game the PFS files are for. I know of two types of PFS files, ones that are uncompressed, and ones that are compressed. For example, the BL game Galtia uses Uncompressed PFS files, and the Otome game Norn9 uses compressed PFS files.