I’m aware that if I install FGII now, it will recognize my FGI key and use it (I haven’t updated yet, because of my custom ruleset for FGI).

But will this work the other way around? If a friend of mine buys FGII (because version I isn’t sold anymore), can he install FGI with the license key of it and join my game?

And before anyone suggests, I will upgrade my ruleset to FGII eventually. When I have the time and energy.