Apple support was not able to assist with reinstalling Mac OS on an older laptop because they don't understand that the code was written that in order to install the OS app on a computer the downloaded OS needs to be the same or older than the OS

Apple support was not able to assist with reinstalling Mac OS on an older laptop because they don't understand that the code was written that in order to install the OS app on a computer the downloaded OS needs to be the same or older than the OS on that computer! Simple right? well, the tech could see the downloaded package in my downloaded folder and thought I could install it onto a USB drive only, the package needed to be opened, run to be parked in the application folder so that from there it can be launched. so having a new computer I kept receiving an error that I could not run the package due to the newer os on it.

The fix was to find an older computer running Sierra since that was the OS I wanted, download the package and run it on that computer so that it is a ready to install as an app, plug in an external drive containing the drive I wanted to use on the older Mac ( I placed it into an enclosure with USB plug.) then run the app from that Sierra laptop choosing the external (formatted GUILD Mac OS extended journaled) drive as destination and wam, it installed it directly skipping the USB step.

The older laptop could not do a recovery/reinstall from the internet for some reason so the only way was to download the OS and install. The original plan was to use a SUDO command line inside terminal to create an install USB drive but that could not be done from a newer computer...

so with an older hard drive in my older laptop running Sierra I downloaded Sierra and ran the package as if installing which simply makes an app in the application folder, from there I plugged the external drive and ran the app, it asked me where, saw the external drive ready, choosing that, it installed it. I verified the install by booting to the external hard drive (alt key on start up) and saw it worked, now I can plug the new hard drive into my old laptop and it'll be ready to use by someone in need of an older but goodie laptop.