[2022] Question about PC Game Pass

1. Is my PC Game Pass enough, or do i need the Xbox Game Pass Ultimate?
2. Will the game release at the Xbox App and Ubisoft Connect?
3. Is the game "cross platform" between microsoft and ubisoft?

My idea is to start playing with the game pass, but i don`t have it always. If i like the game i would like to buy it on the ubisoft store, because i like it more.
If my progress will be always saved at my ubisoft account it will be no problem i think. But if the xbox and ubisoft version are not connected together i will have a problem :)