Is there a way to query and find out the version of Vertica installed?

It can be found here: https://www.vertica.com/docs/latest/HTML/index.htm#Authoring/AdministratorsGuide/Diagnostics/DeterminingYourVersionOfVertica.htm

db=> SELECT VERSION();
              VERSION
------------------------------------
 Vertica Analytic Database v9.1.0-2
(1 row)

Edit from the comments: hopefully a link to a permanent page, which will not become obsolete when new versions come: https://www.vertica.com/blog/version-vertica-running/