What is the concept of flight box in pattern flying ?
Is there a box physically drawn on the ground or are there people who moniter the box like in pylon ... the people with flags ...
Or is it just a virtual box for the judges ?

In according to FAI-F3A rules, 'box' means the frame which aircraft being flied in. From center line, 60 degree at each sides.
Top height is also 60 degree. Flight distance is about 150 to 200 meter from pilot. If the aircraft fly out of the 'box', minus point will be given.
So, pattern flying must be performed in the 'box'.... And, it is very hard.....

What happens if you go out of the box ?

Minus point will be given. The rule is one point per ten percent.

Next question is : Is there any bonus for using scale planes ? extra 300 , ultimate bipe etc ...

As I know, there is no advantage point for using scale planes.

Next Question : If a piece of covering flies of the aircarft ... even then the pilot is disqualified ?
as i read somewhere that if any part drops ...it results in disqualification.

If any part drops during flying, aircraft should be landed immediately. And, point after the moment of dropping, will be given "0".
If any part drops during flying but, pilot does not recognize and judges do recognize, and flying be performed to the end,
judges will check the moment of dropping on their board and after landing the aircraft is checked. If somthing dropped, point will be given "0".

next question : Is nitro allowed in the contest ?

As I know, there is no limitation of nitro.

next question : suppose i took off from right to left because of angular cross winds ... after performing half the seq.. the wind direction gets opposite and my head wind and downwind directions change. In this case will i make a dummy pass to crrect my manevours ? Will i land according to the orignal position (right to left) or according to the new direction (left to right) of upwind ?

If wind direction change during flying, flight schedule must be performed according to first direction. Dummy pass is not allowed.
During landing, you can do the dummy pass and land to the upwind, only if the chief of judges permit and call it.
If there is no call of chief of judges, you must land the aircraft according to the first wind direction.

I hope my answers will help you.
Sorry for my poor English.....