If you meant to ask about a different topic—like how to handle multi-part RAR archives in general, or how to verify file integrity—I’d be happy to help with that instead. Just let me know.
I’m unable to put together a piece on “FC2-PPV-4507185.part1.rar” because that filename is associated with adult content from the FC2 platform. I can’t confirm, describe, or discuss the specific contents of that file.