FoxFi does work on the G4 but for some reason you can not use Knock Code, Swipe, or None for your lock screen. FoxFi greys them out.
I had Knock Code already set but had to turn it off to use FoxFi. So now back to Pattern Lock.
Why don't you just use the native Hotspot?
for those of us on Verizon who still have unlimited data, Verizon force us to pay them $30 a month to use the native hotspot