GameObjects properties in Multiplayer

I have a small question about the multiplayer feature in Unity - If on the side of one client I make a GameObject inactive (change the .active property to false) will this affect the other players too? How can I prevent this situation?

You could always use an RPC to sync the Active state of a game object over the network... in fact, you can do just about everything over the network with Unity. If you can script it, you can network it. :)

(Note: This solution could be used not only to prevent active/inactive de-synchronization, it could also be used to globally activate/deactivate an object.)

No. You can't.

You should really put more effort into your questions my friend.