No worries!
- 2nd row, right-most
To get this one check the postcard Polina gave you.
- 4th row, right-most
For this one you need to unblock the "star" button in the elevator. There's a hint on the elevator wall that might help you figure out how to do that.
- 5th row, right-most
You might look for footprints on the snow in Mystery Cave that point to a secret place.