How can one "force" open needed 32-bit applications on 64-bit OS Catalina?

You already have the correct answer: Catalina requires 64-bit apps and does not support 32-bit apps.

Which means you will need to wipe and re-install macOS Mojave or similar, or install on external storage as suggested above, either of these if your Mac predates Catalina and can support booting from an earlier macOS version. Or you will need to install a hypervisor, and load Mojave into that, and run your app within a Mojave guest. Or find a replacement for the 32-bit app(s).

I believe that what you want to do is not possible under Catalina. If your computer came with an earlier OS like High Sierra or Mojave, you could create a bootable earlier OS such as High Sierra or Mojave on an external drive and boot into that. I'd suggest an SSD for that external drive to keep it fast.