Travel access is not quest availability
Storm moves the story to Kuttenberg; later caravans let you revisit Trosky. Returning to a region does not resurrect characters or reset decisions. Treat your journal and the specific quest prerequisite as the test.
A short pre-commitment check
Record unfinished companion, rescue and faction quests. Visit their givers, finish active objectives you care about and keep a save separate from your newest autosave. For an achievement attempt, record progress before advancing.
After the ending
Free-roam remains available, but it does not preserve every pre-ending activity. Loading an earlier main-quest save can recover missed opportunities at the cost of replaying later progress. Keep the older save until you have checked your intended route.