1. Hearth & Home came out in September that was rebalanced later with another patch. They made it so all foods gave a focus on stamina or health. Also a few other mechanics changed like the way stamina works with shields. The update also introduced some new objects.

2. Recently, they added abominations to swamps and root armour, while made some extra tweaks. Tamed wolves no longer howl. Abominations will appear in existing explored swamps.

3. Mistlands content is coming Q2/Q3 in 2022. Mountain caves and content is coming in Q1 2022. Mistlands content will only appear in unexplored Mislands biomes. Existing explored Mistlands biomes will continue to be empty or as you found them.

4. Character and world saves are still in separate folders. So yes, you can still transfer items between worlds.

You can read about their news here: https://steamcommunity.com/app/892970/announcements/ - More specifically the patches and development blogs.