The builds in Heroes & Generals are named after various generals following the alphabet. This is because it is easier to remember that you are playing a build named 'Rommel' or 'Patton' than 'Build 98765'.
The changelogs moved to the official forum here: http://forum.heroesandgenerals.com/viewforum.php?f=63 and are named "Name of update" - Changelog
Here is the Hallowes Changelog: https://heroesandgenerals.com/2016/11/hallowes-update-changelog
Here is the Young Changelog: http://forum.heroesandgenerals.com/viewtopic.php?f=63&t=54169
Previous Changelogs has been moved to their own page.