Spoiler limitations: The B744 does not recommend using spoilers with greater than flaps 10 or 20 (depending on manufacture/mod status) due to the spoiler turbulence causing cracking in the flap tracks. At the higher flap settings, there already is a lot of stress on the flap assembly (AFM note not to use for extended periods), and spoilers add extra stress to the system. Also, after flap 20 extra drag is available with gear down. If you did select flap >20 plus gear plus spoiler you would virtually fall out of the sky and potentially kiss the earth with a hard smack (as well as cracking flap tracks).
Spoiler or Speed brakes?
744 Spoilers go up and down as the result of a control wheel input and has no bearing on flap position. From memory 744 have a "blow down" valve in the spoiler actuator that lets the spoiler be pushed down from air loads should the pressure inside the actuator exceeds 4000 psi.
Speed brakes on the 744 do operate differently depending on the aircraft config and may have limitations in flight but I would not know as I only fix them......