Games compressed in any way requires a decompression before playing. The installer made for that will do that.

7zip, an existing and trusted executable, can do that. And probably as efficiently, if not more.

The multi part rar file is to share files on the internet with the least possible amount of error.

You mean on usenet or normal file downloads? Torrents don't need such janky workarounds like multipart rars, they redownload any corrupt chunks, not the entire file.

The iso emulates a CD file for installing games, burning the game to a CD/DVD/usb etc for sharing. Also for compression.

Do you also use the cigarette lighter in your car for lighting cigarettes, or anything other than charging accessories for that matter? And stop it with the "for compression" nonsense, it is mathematically nonsense that you could compress a stream of 1's and 0's that has already been compressed.