The (Booster) mesh can have any name, like 'Stage-1' or 'Cylinder01' as long as it matches.
(BoosterNodeName=Cylinder01) in the WeaponsData.ini. To make other things (Other meshes) disappear depends on what function it serves.
LandingGear can disappear when retracted.
Air brakes, inside nodes,
You can fool the game a number of ways, but it has limits. Look at the Me-163 Comet the Gear falls off, until it's extended again. Another trick is to animate a mesh to move to the inside of the model, you can control it by Assigned ID, or use a AerodynamicSpeed statement trick. Like I said
, it depends on the meshes function. One of the most important things I've lerned is the 'hierarchy' of the meshes in 3DMax to make things do what you want them to do. One other thing, the position or proper function of a mesh in game sometimes depends on how it's exported. Example is a Rear firing machine gun,(tail gun) it has to be exported facing forward to be correct in game, I spent a few days pulling out my hair to get the Storch aft gun to work correctly.