So happy you're enjoying the game so far! Let me help you out.
SPOILERS BELOW
The password to Brandy's laptop is something that is/was important to her. Try searching around in the upstairs hallway and Brandy's bedroom for hints about what it could be!
As for the alternate dimension, I'm assuming you're talking about the master bedroom door, right? You'll need a key and to specifically type UNLOCK DOOR before you can enter the bedroom.
Let me know if that helps! Feel free to reply again if it doesn't!