It's handy to have an external, bootable macOS Ventura installer, but you practically have to fight Apple to make one. Here's what you have to do.

This tutorial shows you how to create a bootable macOS Big Sur USB installer drive, which can be handy for performing fresh installs on your Mac.

* For many years a Mac boot disk was what barefootguru described; an external disk that could boot a complete version of the Mac OS. This was very useful for 3rd party disk utilities for recovery ...

To create a bootable optical disc (or, similarly, a bootable Zip or floppy disk) was a bit more involved, but not by much. So how does all of this compare to the situation with Mac OS X today?

The easiest way to revert is to install an older, compatible version of OS X on an external drive. The 2011 iMac models have USB 2.0 but also FireWire 800.