The regenerating big mushrooms in the farming II area does not give farming xp 

you can buy diamonds and emeralds in the bazaar and sell them to the marketplace for easy profit, it ruins the economy note: I have not checked the other items in the bazaar

If your inventory cannot hold the nine stacks of ingots or gems that come out of crafting a block into ingots or gems then when you pick the ingots or gems up again it will count towards the total collections and allow you to unlock more recipes  Edit: If you put anything in the custom crafting table, have your inventory be full, then exit the custom crafting table, you will get collection points upon picking the items back up

Armor sets do not give the set bonus if any of the pieces in the set are reforged. They do give the set bonus back once every piece in the set is reforged though.

7. you can craft items without unlocking them in the collections (it worked on enchanted diamond block and I have yet to try something else)