Death's Door

• If you care about completion, use every plant pot even if you don't need it, you'll find enough seeds and one of the postgame challenges requires you to have planted a seed in every one of them. No, there's no map or any way to know where the ones you missed are.

• Sewer manholes (crowholes?) look like places to use a future movement item, but they're not. You just need to slam into them (press Attack while falling); yes, that does mean some holes are exit-only, since you'll have nowhere to fall from. This is accessible from the start and the game will not tell you about it.