Steam preorder code for Steam base game invalid in Mog Station

[worldofneil]

But with that prepurchase rewards code we can still play early right?... If it says we can put it in on june 20th thats 4 days late of when we need to be playing?

If you mean the early access code, then yes if that's been successfully applied to your account then you can play from the 16th. That code will work temporarily through to the 23rd. The full Stormblood code (both regular and collectors) can be entered after 20th June, but must be entered before 23rd June if you don't want any interuption as that's when early access code stops working.