Fortnite - warning DO NOT play on PS4, or you can't play on Switch (and quick start guide if you're sheltered like me, and didn't know about this game before)

[irstupid]

Curious as to this scenario.

Let's say I'm a PC/Mobile player only. When I go to play crossplay, do I choose who to crossplay specifically, like I say I want to crossplay with PS4 players, or Xbox, or Switch, or Mobile, or does it just toss me into a lobby and I don't actually know what systems I'm crossplaying with. It could be from any system and no way of knowing unless I ask people over chat what systems they playing on.

Now let's say I logged into the PS4 once to get a skin. I never play on the PS4, and only the PC still. Can I no longer crossplay with Xbox/Switch people ever again?