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 

@Colin Brough - values for Cache Server manager are stored in the registry.  If these servers are using CCR, you can actually download registry keys directly from you CCR System page (above Environments select Export > Studio) and load it onto a developers desktop in order to have the Environments automatically show up in the Caché Server Manager.  If these are not CCR-controlled, then you can create a .reg file similar to the following in order to pull them in (this was generated by CCR for an internal System and I have modified a few fields; the last two entries change Studio to have a red background on LIVE to make it easier to see where you are located):

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\InterSystems\Cache\Servers\ISCU-Demo-BASE]
"Address"="base.demo.iscdemo.com"
"AuthenticationMethod"="0"
"Comment"="This has been created by the CCR system export."
"ConnectionSecurityLevel"=""
"LastNamespace"=""
"Port"="51773"
"ServerType"=""
"ServerPrincipalName"=""
"Telnet"="22"
"WebServerAddress"=""
"WebServerInstanceName"=""
"WebServerPort"="443"
"HTTPS"="1"

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\InterSystems\Cache\Servers\ISCU-Demo-BASE]
"Address"="base.demo.iscdemo.com"
"AuthenticationMethod"="0"
"Comment"="This has been created by the CCR system export."
"ConnectionSecurityLevel"=""
"LastNamespace"=""
"Port"="51773"
"ServerType"=""
"ServerPrincipalName"=""
"Telnet"="22"
"WebServerAddress"=""
"WebServerInstanceName"=""
"WebServerPort"="443"
"HTTPS"="1"

[HKEY_LOCAL_MACHINE\SOFTWARE\InterSystems\Cache\Servers\LIVE-ISCU-Demo]
"Address"="monitor.iscdemo.com"
"AuthenticationMethod"="0"
"Comment"="This has been created by the CCR system export."
"ConnectionSecurityLevel"=""
"LastNamespace"=""
"Port"="51773"
"ServerType"=""
"ServerPrincipalName"=""
"Telnet"="22"
"WebServerAddress"=""
"WebServerInstanceName"=""
"WebServerPort"="443"
"HTTPS"="1"

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\InterSystems\Cache\Servers\LIVE-ISCU-Demo]
"Address"="monitor.iscdemo.com"
"AuthenticationMethod"="0"
"Comment"="This has been created by the CCR system export."
"ConnectionSecurityLevel"=""
"LastNamespace"=""
"Port"="51773"
"ServerType"=""
"ServerPrincipalName"=""
"Telnet"="22"
"WebServerAddress"=""
"WebServerInstanceName"=""
"WebServerPort"="443"
"HTTPS"="1"

[HKEY_CURRENT_USER\Software\InterSystems\Cache Studio\Editor\Server Background Color]
"LIVE-ISCU-Demo"=dword:00a0a0ff

[HKEY_CURRENT_USER\Software\InterSystems\Cache Studio\Editor\Status Bar Color]
"LIVE-ISCU-Demo"=dword:005757ff 

Hope this helps!

Ben