Error message and button problems(see attach flash file)

Hi
Let me briefly explain what I am trying to do.
I have four label which are main, commercials, facts, and shop.
I want  first to frame 29 to animate and stop frame 30.
In the frame 30, there are four buttons which is a main menu.
Please see the original layout at http://www.funrise.com/flash

Here is a quesiton 1.
On the label "facts"
prev_btn is not working and next_btn is not working. Please help this here.

Here is a question 2.
On the label "commercials", there are three FLVs and it runs automatically when user visit there.
So after user visited that page and move to other page. I want to stop the video.

Here is a question 3
TypeError: Error #1009: Cannot access a property or method of a null object reference.
      at sample_fla::MainTimeline/frame30()
Do you know why I am getting this error message?

Last question.
I don't know why this sample flash doesn't stop at frame30.

I am attaching this sample flash file here.
Hope you could help me this problem.

Thanks,

p.s. please delete this fla.txt extension after you downloaded.Start Free Trial