1. Same answer as when we
discussed this in the SP forum: Not possible (the only difference is that in MP individual players can use their own flesh skins, for face and hands only, assuming that is enabled on the server. Same with clan arm-patches and vehicle badges).
2. You can't do it directly, but you could have a "start siren" and "stop siren" action which caused a siren sound to be played on the vehicle using
say. Remember that you'd need to use this command on every client machine since
say is local only.
3. Not if you are just updating the position on a single machine. You'd need to update the position on every client machine every frame (ideally using
waitUntil) to get this to work properly and not jerk about due to lag.
Please don't ask questions in a thread that are not linked to each other or mentioned in the title. This makes it easier for other readers to know which threads to read for answers to their own problems or for the "experts" to know which ones they could give answers to (it seems reasonable to ask both the siren and lights question in one thread though, since they are both linked to "adding a flashing light and siren to a police car").