Beyond.a.steel.sky.v1.5.29158-plaza.part3.rar -

.part3.rar – This indicates the file is not a standalone installer. You need all other parts (part1, part2, etc.) in the same folder to successfully extract the game. Installation Instructions

v1.5.29158 – Includes various performance updates and bug fixes released after the initial launch. Beyond.a.Steel.Sky.v1.5.29158-PLAZA.part3.rar

Right-click on Part 1 and select "Extract Here" using a program like WinRAR or 7-Zip . It will automatically pull data from part3 and the others to create a single ISO file or folder. Right-click on Part 1 and select "Extract Here"

If an ISO is produced, mount it to a virtual drive. Run setup.exe to install. Run setup

PLAZA – A well-known scene group that specializes in "cracked" game releases and updates.

Since this is a "scene" release, your antivirus might flag the crack files as "False Positives." It is standard practice to exclude the game folder from scans if you trust the source.