Close. Lessers *must* be placed within 6" of an icon when they come out of reserves, but they do not scatter. If there are no icons on the table (or the only icon also arrived from reserves this turn) they they cannot appear and are destroyed. If the icon is inside a transport then the daemons appear up to 6" from the hull of the transport.
Lessers always come within 6" of an icon and never scatter.
When greaters arrive from reserves, you must select a champion, sorcerer (regular or aspiring) or lord for it to possess. Icons do not matter. Pick one of those characters and he possesses that guy as outlined on p61
If there are no such characters on the board then the daemon is destroyed.
If the chosen character is inside a transport then the model immediately deploys up to 2" away from an access point and the daemon appears there.
It's all spelled out in the boxed text on p61 of the new codex. If you need help or advice on anything else, just ask.