Sometimes I will accidentally place a hatchery tile where I meant to place a treasury tile. Is there a way to undo this or remove this tile? Or am I just stuck with it once it has been placed?

If DK 1: In the same menu as the rooms, click on the $ sign to sell things.

If DK 2: In the bottom left corner, click the dollar sign to sell stuff.

Ohhhhh. I never even thought notice that $ was there let alone that it was a button. Thank you!

Glad I could help!