If you cannot get your old account back it may be worth talking to @reward.app to see if they can send the outstanding rewards to you. You may need some proof of ID. You should do a new picture with your new Hive name.

UPDATE: I see people already removed the rewards on your old posts to stop the crooks getting them.

Unfortunately a lot of people have been caught out by this scam, so spread the word about it.

The main lesson to learn is not to give out your master key. That should only be used to change your keys. No site should ask for it otherwise.