Furyou Miko wrote:This is the wrong forum - you want the one below, Official Rules (or something like that).
Also, you're looking at the old book - in the new book, individual models buy Marks, which then unlock Icons.
What? Battle Reports?

You want the Forum above: You Make Da Call.
Although I never had it, your question seems more applicable to the old codex. However...
1. The Icon applies to the whole squad. To take- for example an Icon of Khorne, the squad must also have the Mark of Khorne. It applies to a character in the unit if he also has the correct Mark.
2. The Icon of Chaos Glory has been replaced by the Icon of Vengeance. This doesn't require the squad to have a Mark and gives them Fearless.
Your question seems confusing so I'll try to help:
Marks: these apply to each Chaos God. They give rules that represent that God's specific 'abilities'. Characters and Infantry can purchase these Marks which if at all bought, MUST be bought the same one for each model in the squad. Also, the Icon must be allocated to a model in the squad, if that model dies then the ability is lost, unlike the Mark where it is part of every model. And... don't forget they add 1" to your charge range.
Icons: these give further abilities to the squad with the correct Mark or Icon of Vengeance if Undivided. This ability is also gained by a character joined to the unit if he has the correct Mark.
Hope this helped!