If it's only a few KB but claims to be a full game or program, it is almost certainly a virus.
is not a known software product or public service; rather, it is a specific compressed archive file that someone has likely shared with you or that you found online. Because ".7z" is a container format, its safety and value depend entirely on what is inside it. File Overview
or what it's supposed to contain? Knowing the source would help in determining if it's safe to open.
Usually, files with random or specific shorthand names like "B1qwer" are used for private data transfers, game mods, or software patches.