Can some version of python not run on some version of Raspbian? Is there some thing in the architecture of some version of Raspberry Pi that could make them incompatible with some versions of python?
I'm curious what you might be encountering, because I have installed the latest versions of Raspbian on my oldest RPi devices and I haven't experienced any issues.
Supported Python Versions can be found here: Python Wiki
Running different versions of python is not an issue of the hardware, means version of a Raspberry Pi. It is an issue of the version of the Raspbian distribution. A specific python version is integrated into the distribution with its shared libraries and tested that it runs there without dependency and version problems. Raspbian Stretch comes with python 3.5, Raspbian Buster comes with python 3.7. You can install Buster on all Raspberry Pi versions and have python 3.7 available but installing python 3.7 on Raspbian Stretch will not work out of the box. Mostly you have to compile it from source to match the different shared libraries from Stretch. This process is called backport. For Debian you can find precompiled backports at https://backports.debian.org/.