yes it will.
Use poplar for bed slats.
Yes you could, if your planer accepts the size
They can be used for finish trim I did but sanded them and sealed them before installing them
I suppose that would depend on what kind/size animal you are talking about.
I would use a 1×3 if you have the room or the 2×2
Yes, I have used them for that purpose. I just use a hatchet to 'sharpen' the end of the board that goes into the ground. They work great for tomatoes and all, as long as the board doesnt have a large knot in it which is a weak point.
A white wood like pine.