We update Redmine and all its components every time there is a new release of Redmine and we publish that version of Redmine in bitnami.com however you can ask for that version of the installer every time you want to install it.
Please note that we don't update the components of the Bitnami installer for Redmine 3.4.2 so if you install this version of the installer in the future it will have outdated components. In case you want to use the latest updates of all the components you will need to install the latest version of the Bitnami installer.
Regarding support questions, you can always ask in this community forum, no matter the Bitnami Redmine version you use.
I hope this information helps