If i want to use cycles full bake in a game engine, i should assign simple diffuse shader to all objects and force them not to cast or recieve any game engine lights. Is is true, and what kind of shading cycles uses in texture viewport mode?
If you bake full-render textures, you should use a shadeless material (or emission) to apply the baked texture. A diffuse shader will still inherit basic shading information which you don't want.
And yes, you don't want them to cast shadows or receive game engine lights.
I'm not sure what you mean about the "kind of shading cycles uses in texture viewport mode." Probably GLSL.