2 questions

[Sa-x]

1. How to make fof on a fof (2 fofs on only a sector)
2. how to make the shadow at the pit, the shadow begin lighting and at the end is dark

 

[Kyasarin]

1. Create a Control Sector with the heights you want for your FOF (floor = bottom; ceiling = top), and tag one of that Sector's Linedefs to the in-game Sector. The action you give the line (100, 123, 200, etc.) determines what kind of FOF there is.
2. Same as how you make a normal FOF, but it must be a light block. Control Sector darkness is how dark that area is.

Note than just about anything applied to the Control Sector effects the FOF, too.