Hi!
Can I insert an animation frame-key for a single vertex in a object in Blender?
Blender does support RVK’s which are relative vertex keys, but unfortunately the game engine does not support them. You can either use armatures to achieve the effect you want, or you can program you’re animation from python, which can animate the mesh.
Unfortunately, the morphed mesh through either of these methods will not morph it’s collision values, so it’s collision mesh will stay the same as the original.
Thanx!! 
Well I guess I have to learn the armatures system!
Btw is it possible for two object to have the same vertex??? I suppose it isn’t but it would be great when animating in games…