Previous saves won't work with the new versions.
However, when making a new game, you can jump straight to the latest content and select the choices you made.
There will be a main core ending that I assume most players will aim for. But that ending will change slightly depending on how the player gets to the ending.
For example, someone might get to the ending with Lily as their slave, while someone else might get there with her as their wife. There's also choices in this game, which kill of certain girls that can affect who is there at the end.
And depending on what happens to the Goddess too, will also change the ending.
As for completely different other endings besides the main one, there are already other endings in the game. But alternative endings in this game are usually bad endings.