How to check for upgrade availability? Check for regular redemption availability. If there is Saver or Advantage seats available for pure miles redemption, it means there is a high chance upgrade availability is there because they supposedly book into the same class - I and D respectively.

You can choose to waitlist for upgrade, but this can only be done offline (call or live chat) - be sure to emphasise you want to waitlist for an upgrade award and not a redemption booking award because they would otherwise tell you they can't do waitlist for you - but that is only true for redemption booking waitlist. Their website does not support upgrade waitlist so the agent should be able to do it for you.