click light in ceiling

there is a spot in between the jail bars that you click an it gives you a view outside the bars, the key is there. Use your magnet/rope combo to get the key
SPOILER: (click box to reveal/hide)

the key you get is not for the cell door! Combine the blue thing with the metal bar you got in the hidey hole by the bed and you get a screw driver, use that on the hinges of the door to open it
SPOILER: (click box to reveal/hide)

in the office with the pc is a scale, use the marble you got from the outer room (for lack of a better discription it was hidden on top of the "boiler" on the left side of the room) and the marble you get when you click above the pc along with the shoes you picked up in the cell
SPOILER: (click box to reveal/hide)

you have to click down to go to another part of outside

... it goes inside the gun which you use...

... to shoot the balloon outside.

I've put the ring in the cash box (?) but I don't know what to do next. The door is asking me for a code, but the one from the computer won't work

You have to click on a corner of the bed for that (pillow side). The corner's in the same frame where you get...

... part of the screwdriver.

under the rug when facing the computer

The other ball is on top of the desk next to the computer, when looking at it from above (the same view you get the gun from) it looks like a group of smaller balls, to me, but it's the one ball reflecting light or something...
HINT: (click box to highlight/fade)

Click on pillow on bed.
Click far right edge of bed and pick up wooden shoes.
Click down arrow once.
Click lower right of light grey box. Click box again after it zooms in. Pick up forst piece of screw driver.
Click down arrow twice.
Click Window and pick up chalk.
Click down arrow.
Click light, pick up magnet.
Click sink and pick up soap. Click sink handle and pick up note 1. Shows the number 30.
Click right arrow.
Click bottom of trash can, pick up rope.
Combine rope and magnet.
Click right arrow.
Click between bars next to hindges on door.
Use magnet with rope to get key and second part of the screw driver.
Click right arrow.
Combine parts of the screw driver.
Use screw driver on screws on door. May need to click twice.
Click on the opening in the door.
Click on 2nd pipe coming out of the box in the corner. Get the silver ball.
Click down arrow.
Click on the upper right corner of the carpet and pick up the arrow.
Click on the wall tot he right of the computer.
Pick up gun and grey ball.
Click up arrow.
Use both balls and shoes on scales. Pick up bullet.
Click wanted sign. Get number 300.000.000.
Click down arrow.
Use dart on dart board.
Click on door to the right.
Compine gun and bullet.
Use gun on the balloon.
Pick up coin.
Click down arrow.
Use coin on glass door.
Pick up bone.
Click on the large spinning fan. Pick up the DVD.
Click the left arrow.
Click on the door to the right.
Click the down arrow.
Use the DVD on the computer.
Note number 36.
Click the down arrow.
Click the door to the right.
Click the down arrow.
Click the right arrow.
Give the dog the bone.
Click on the door.
Click the 3rd button on the radio twice.
Pick up Note 2. Number 33 shows on the note.
Click the down arrow.
Click on the strips in the painting on the wall to the left. Pick up purple jar.
Use chalk on the pool table.
Use purple jar on the pool table.
Pick up ring.
Use the ring on the cash register.
Zoom in on the numbers and it shows 0.34.
Click on the door in the back and enter the code 23363433 and thats it.

If you combine it with the rope before you attach the magnet you can make a noose and hang yourself from the light in the cell

He forgot to mention that u need to use the key bfore you can input the code for the door.