The space+ seats are reserved for Koru, Gold and Elite members. Unless you have status there is nothing you can do to get one of these seats except hope that there might be one free at checkin and staff will move you, the odds of which are realistically pretty low.

Access to preferred seating is not a *G benefit but Air NZ do seem to allow *G access to these seats if they ask (they used to be able to select them for free).

The back rows are blocked on every flight and typically opened up St T-48 if not allocated prior.