Well if they never get solved are they hard or are they impossible?

What’s the difference between, “It was hard and we didn’t solve it” and “It was impossible”?

You are aware that no problem was solved before it was solved, right?

Well no, you often can actually. You can have positive information about the impossibility of something, for example the prospect of winning a chess game after losing your king. You don't need to play billions of games of chess to see whether it's possible.

Zoning changes happen all the time. Tax changes happen all the time. Subsidy changes happen all the time.