I wanted to see episodes from seasons 1 to 4 where we get to see Cory's parents and Topanga parents hang out together. It never happened. I guess they were not friends?

There was one episode in which Cory and Alan talked about playing against Topanga's father in some baseball game in Season One and the Matthewses did host the Lawrence parents as guests for Mr. Feeny's wedding (Season Six) as well as having them participate in Cory and Topanga's wedding (Season Seven). However, it seems at best that the Lawrences and Matthewses were civil to each other for their children's sakes (and considerate of notifying each other when they though they might need news about their respective offspring) but were NOT actual friends. While it would have been nice for the four to have become friends, it doesn't seem to have happened but at least they stayed civil with each other and neither side tried to sabotage the other (or the other's child) which is more than many sets of less-than-friendly in-laws can say.