difference between games?

[Black Fox]

we were here
we where here too
we were here together

These are all separate games with different levels and stories?
Is there like a base game (we were here)
then the base game + levels (we were here too)
and then base game +levels + extra levels (We were here together)

Trying to figure it out.

[Kiryu]

3 completely separate games with its own puzzles and stories

basically we were here 1, 2, and 3

[MacCekko]

Hello!
I have this game in my Steam Library (We Were Here 1) on PC, and I was wondering if I could play along with my niece who has it on her XBox (via her Xbox Game Pass account) at her home. Seeing from the devs portal, it seems we cannot: crossplay is allowed but between the same kind of platform, so PC-PC and Xbox-Xbox even if of different generations. So the whole thing is unclear to us. Do you have any suggestion or piece of advice?
Perhaps if I bought it on MS Game Pass Store (I have the Game Pass for PC, so I might buy it a second time), would then this option become available for us two?
Thank you.