To prevent losing quest items, it is strongly recommended to turn them in before starting another raid or transferring them to the quest item special stash in the "Quest items" tab of the "Tasks" tab if you do not want to continue the quest in the next raid (e.g. during Delivery ...
For the Arena, see Arena Changelog. This page contains a collection of official patch notes for Escape from Tarkov. It's not complete, and it has to be noted that the developer Battlestate Games intentionally doesn't announce every change to keep surpris