Can you move Flaming Sphere to a point you can't see?

Question

Let's say you are outside a room and the door is open. You cast Flaming Sphere inside, on a square you can see through the door and then move away so you no longer have vision of the sphere.

On the following turn, you choose to sustain the spell. When you do, can you roll the ball, for example, 10 feet to the right, even though you have no vision of the ball nor the place you are moving it to? What if you can still see the ball but you can't see the place you are moving it to, but you know the dimensions of the room? And what if you don't know the size of the room, can you move it 30 feet to the right? What happens if it hits a wall?

Answer 1

As far as I know, you don't even need line of sight to cast Flaming Sphere, lest to move it.

Spells usually require a line of effect:

When creating an effect, you usually need an unblocked path to the target of a spell [...]. Visibility doesn’t matter for line of effect [...].

So it would be perfectly valid to target an unseen point behind a wall, at the condition that there was an open door or window between the caster and the effect.

A similar case can be made about moving the sphere: moving it can be seen as "creating an effect", thus requiring a line of effect, but there isn't anything there that would indicate the need for a line of sight. Whether you know the dimensions of the room doesn't seem to matter either.

Of course, without sight you are casting/moving your effect blindly. I don't think there are any guidelines about how a DM should handle an "illegal move" (like trying to make the sphere go through a wall), but I would rule it that way: the sphere stops when it enters in contact with the wall. The caster gave an impossible order, so it didn't happen. Quick and simple. Of course, since the sphere can't communicate, the caster wouldn't know that the sphere stopped.