can i close a region?
I don't think there's any way to actually close a region, except that if all of its members leave it should cease to exist.
I'm not entirely certain though.
Well if you wanted to close Chaos2 your current region. Just make sure no one else comes in (which looks like you password protected it so they cant) and then leave the region. And like the post above mine, when there are no nations in a region at the Update time (sometime within 1 day) then the region will cease to exist.
If you're the founder of the region, you can just kick/ban everyone out and give the region a day to die.