I apologize for not responding to your post more fully. Now I will try to answer each point.
1. The "New Game +" mode skips all the quests of the previous version. New quests will not be skipped because they are NEW. This is done so that players, when playing previous versions of games, can play new content by skipping all the quests at once.
2. When you skip quests, you won't unlock all the scenes, because this is sometimes done separately from the quests. Therefore, you need to finish the entire gallery manually.
3. Right, because you released the alternate version quests. The new version includes new quests that cannot be missed yet, until the release of the next version. Therefore, go through the quests and you will meet the Blacksmith's House and your house.
4. No. There is no need to skip this scene, because we purposefully left this plot twist so that the player, having replayed it again, would remember those moments that were further along the plot. The new version has additions to the main plot, which is why we decided not to miss this moment.