Good questions.
1. It is not exactly like FNAF, you can still move but the space you're in is really small and you won't have much time. So the player will learn that moving around isn't always a good idea & they should stay behind the computer. However moving isn't completely useless, there are certain random events that can happen and force the player out of the sit, or when the 'cursed' props get too close, the player has to leave the computer for a few seconds.
2.If the props sneak their way behind the player and make contact with it, then it's game over. Some events can also kill the player.
3.haha, no. The computer is one of the core gameplay mechanics of the game. I made the computer model early in the game to make the devlogs entertaining. This doesn't mean that the reason computer exist is to be entertaining for people watching the devlogs. Each level the computer will be filled with some tasks that force the player to finish them before the deadline while avoiding props.
In summary, the computer is mostly a distraction that forces the player to look at it, in order to let props get closer.