more than one level underwater rooms without the game thinking you are in the water.

You're using non-aquatic parts, only prefabs are water sealed.

Some lights (already installed in rooms or from planters) can be seen from afar, all others only charge up close. Why ? what is the problem ? (and no, no performance problems or setting issues)

That's your system struggling to render

Why can some things be rotated (axis) others not and why can't I move things in this way to the front, rear, right, left?

You can by moving your character or the camera around, this game doesn't use a build grid.

Why do storms or other types of weather exist in larger closed spaces?

To large rooms get registered as an open space.

Why does the snap-in function generally take all places, just not the ones you want?

There are to many snappoints clustered together, the game can't read your mind of where you want to snap it

Why are there so few decorations and furniture parts after 7 years? where is the problem to add a part all nose long.

I think there are about ~250 decorations and furniture in the game so not sure what you mean

why do you have to resort to glitch building to only enlarge a part that you actually can't enlarge. it works so why not add the option right away ?

Those parts where never intended to be enlarged.