There is no rollback mechanism built into the installer (unless there is an issue in the middle of the installation in which case it will back out the installation).  If you are using a VM the best practice is to snapshot your VM prior to upgrade and roll back to the snapshot if something goes wrong.  This should be done with care because any data changed post upgrade will be lost when you restore the snapshot.  

@Scott Roth - best practice in cases like this is to set the /exportversion qualifier in the DEV environment (or whatever is exporting the source) until all of your pipeline is on the newer version.

E.g.

w $system.OBJ.SetQualifiers("/exportversion=iris2022.1")

This should prevent any newer attributes from being included in the exported XML which would prevent import on an earlier version.  

ref: https://docs.intersystems.com/iris20242/csp/docbook/Doc.View.cls?KEY=RCOS_vsystem_flags_qualifiers