In the Programs and Features, I have old versions of Watchguard Fireware v11.1, V12.1, V12.2, we're on v12.3. Is it safe to uninstall the older versions like the v11.1, v12.1, v12.2, etc.. in the program and features in windows?
Yes it is safe.
The older ones should be XTM firmware for your firewalls.
The only reason that you might want to keep any of these is if you are managing firewalls running with those versions - in case you need to reload the firmware after a downgrade.