dont know about one, not sure about two but for making a night level, changing the camera ambient to a negative value can do alot, camera.ambient=-80; or so on, theres also a sun light variable that affects the ambience of all models, look in the manual...

as for 3, hmmm, you want to trace on the camera.s tilt? well.. thats easy enough:

VECTOR trace_coords;

vec_set(trace_coords.x, vector(3000,0, 0));
vec_rotate(trace_coords.x, camera.pan));
vec_add(trace_coords.x, cam_pos.x);

c_trace(camera.x, trace_coords.x, IGNORE_PASSABLE+IGNORE_ME+ACTIVATE_SHOOT+USE_POLYGON);

the above will trace from the camera in the direction the camera is looking...

well lets hope that was helpful, also most of those questions were addressed in the AUMS, which are quite fun to read through