Using a pkg editor

I recently downloaded a game for which I have been waiting four years, only to find it requires OS Ventura. My Mac is an iMac Retina 5K, 27-inch, (Late 2015) running OS Monterey 12.6.6 and it will not let me install Ventura.I don't know why. I have been trying to get help from the game's forum pages (the game is Cyan's "Firmament") and have received the following reply:

"Hi, I managed to play with Firmament on my MBPro Retina 2015 running macOS 10.15 by extracting the. game app from the downloaded pkg file and changing the minimum requirements of the app. To do so, use a pkg editor like “Suspicious Package” or “Pacifist”, right click on the game icon and choose “Show Package content”, go to the “Contents” folder and open the Info.plist file with TextEdit for example. Then replace the two “13.3” occurrences by “10.15” and relog your session."

I am not technically very aware (I'm 80 years old) and hesitate to dabble in things I don't understand. Can anyone tell me their views on the 'Suspicious Package" software and whether it might help me play my game. The last thing I want to do is compromise my iMac by using unsafe third party software. I will obviously contact the contributor of the above reply in due course because I am unsure of what some of the steps mean, but I thought I would get some input from these pages first.