If you don't get the daily platinum on the first try then you can refresh the page or start searching for a private or quick match then it will reappear when you go back tot eh home screen if you didn't actually get the platinum
While it is possible to get to extremely high levels in the campaign mode of this game and Tiri may be very good at campaign, you should know that Tirikatene is known for using multiple accounts to troll other players and using exploits to make those accounts seem higher level than they really are.
once you beat the first 4 waves the music stops and it just keeps releasing small waves at you like every 10 secs, until you get bored and just stop. score is randomly generated :P