If you buy the place and the basement stove works, just leave it. It's not in the way, is it?Most likely how they got it down will remain a mystery.
Or, if you mean ask about it being removed, we would say something like "remove all (something) and debris" in the contract. I forget what the "something" term is but it means their stuff that they might think is not "debris". And probably not say anything otherwise.
Very, very sadly, no. I started to look up the zoning but dh would very much not want chickens there even if the zoning allowed. The neighbors are very close and very many on all sides. And this is a much more intense job for him so he doesn't want to do any yard work much less build chicken coops or take care of them when I'm gone.
But, this will be three years. With an outside chance of four. Then he will retire and we will move to where ever we choose to go. I expect to get chickens again then.