Answer

+1
Answer
Answered
They're still open. You can access test server via this link: http://test.tankionline.com/battle-en.html#/server=RU7
+1
Answer
Answered
They're still open. You can access test server via this link: http://test.tankionline.com/battle-en.html#/server=RU7
When do they open the game? what is the "invitation code"?

Invite codes are usually not issued to players, they are only issued to testers. I'm not a tester but if I was one, I would give you the invite code because not giving people something is not nice and my level of politeness is the same as Japanese politeness which is very kind although I'm not Japanese.