How can the Antonov AN 225 only have 2 nose wheels?
The reason An 225 has only two nose landing gears (for a total of four wheels) is that it was developed from An 124 Ruslan, which had pretty much the same arrangement. This works during normal operations as the MLG take up most of the load. 

However, for loading/unloading, the wheels are not loaded- the nose landing gear is folded, while a support strut comes out, which provides the necessary support and load carrying capacity, as shown below (thanks to @Federico for finding the image).



Image from airliners.net

In this image, you can clearly see that the NLG is folded and the weight is supported by the struts.



Image from news.yahoo.com