is this full on halo 5?
No.
It's the Halo 5 multiplayer portion, but you can't matchmake with the X-box players (obviously), so it's the Forge maps (along with the base maps?) to be used in "Custom games." I dunno if X-box cross play is available in those.
Edit: Also El Dewrito is still being developed despite the Russian F2P (legit) developer cancelling it with Microsoft. So if you want Halo 3-ish era Halo on PC that's still around but you'll have to look for it.
