There were at least two - one of them was the one where an ancestor of Lois married Baron Tempus and (I think) the US stayed British with Tempus as king - sorry, it's a long time since I've seen that one. They don't say anything about Nightfall in the main Alt universe, which suggests that it was a non-event.
That wasn't an alternate universe--that was our L&C going back in time
in their own universe to sort out a curse that happened in their past incarnations.
The only alt-world that was visited in the show was the one where Lois helped the Clark there to become Superman, and he ended up not marrying Lana Lang. Later on, that world's Clark visited the main L&C universe, when this Clark was temporarily lost.
