You can open or close it as you like, or even take out a few pieces, we took out two because it was too big for our space. If you want to use it to block access to a room, as a singe piece, I would not recommend it. The baby will pull quite hard on the rails and it will topple over. For one door access, I would suggest getting something with fixed points. Something like this maybe: Savic Dog Barrier

Yes, you can open it however you like, each joint folds from 0 to 180 degrees