As applicable to B744
YHZ,
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).
"Jet upset" is basically an "unusual attitude", but especially one at a high altitude (where there is little thrust margin, and little margin between high and low speed buffet). It can be caused by thunderstorms/CAT, autopilot/trim malfunction etc. Recovery is standard. Oh, just keep in mind that underslung jets tend to pitch you up when you add thrust and vice versa.