No. All Tuskgor Chariots have the Mark of Chaos Undivided and only characters bearing the same Mark (Undivided) can ride in the chariot.

During the Remaining Moves step of the Movement phase the turn the brayhorn is sounded. Note that the Beasts of Chaos player sounds the brayhorn, marks his intended entry points, and takes the Ambush leadership tests before the Rally Fleeing Troops step of the Movement phase.

Oh, sneaky! Still, the answer is no. It was our intention that a general who is a Daemon would not have Shaggoths in the same army (even if the Daemon counted as a Beast for army selection).

No.

You cannot choose to remove Ungors instead. If the Gor command are slain, the Ungors cannot pick up the standard or instrument.

No. According to the rules for Beastmen Herds the herd adjusts it's formation when intially charged or charging. It is silent as to the topic of lapping around, therefore the main rules take precendence and Ungors in the "rear" ranks will normally lap around first.

If your unit only touches Gors at the start of the combat, the models with the highest Initiative value's attacks can only score wounds on Gors. This round of attacks can rack up no more wounds than the number of Gors, not counting additional wounds from other circumstances (overkill, etc.). Any killed Gor models in the front rank would be replaced, by Gors if available, otherwise by Ungors. The models with the next highest Initiative value's attacks would then proceed, and those attacking models touching more than one type of model have to say what they're attacking against. Again, attacks against Gors can score no more wounds than the number of Gors. Also, attacks against Ungors can score no more wounds than the number of Ungors. At the Gor's Initiative value in the sequence, the survivors of the original front row (if any) can fight against their attackers. The Ungors would not get to strike in this round of close combat, unless they had models able to strike at the start of the combat round (with spears for instance) that were not killed.

The template only kills the types of models touched, so the wounds are not transferred onto Ungors in this case.

Units failing an Unruly test must charge "if there is an enemy unit that can be charged using the normal rules". When a unit fails a fear test when wishing to charge, the main rulebook indicates that the unit "may not charge or shoot and must remain stationary in that Movement phase". As they are disallowed from charging or moving per the "normal rules', the original failed fear test takes precedence. Basically, Unruly is a drawback, and so it would seem odd if they could charge because of it, when normally they would not be able to.

No. The Unruly rules indicate "if there is an enemy unit that can be charged using the normal rules". When a unit rallies it is unable to move that turn, and thus is not eligible to declare a charge. Basically, Unruly is a drawback, and so it would seem odd if they could charge because of it, when normally they would not be able to. I'd rather not have a situation when a player wants to be Unruly.

Casualties are caused against models in base contact first, so Gors will normally be struck by the chariot first. Any further hits are randomised.

One. "Chaos Armour" is a magic item in the Beasts of Chaos book. Per the magic items section of the main rulebook, "No specific magic item can be carried by more than one model in the army, with the exception of scrolls."

Generally no as characters without the option to wear mundane armour may not wear magical armour, however there is one exception. The magic item "Chaos Armour" in the Beasts of Chaos book states "May be given to a Bray-Shaman". Note that the magic item also states that "A model may wear Chaos Armour and still cast spells."

Mortal characters may drop their Chaos armour to wear the Trollhide armour. The Beasts of Chaos book indicates that mortals may use any magic items not specifically barred in the item's description.

I would say that the attacks count as magical.

In a mixed unit, the models will hit other models of the same type. So, the Gors will all hit other Gors, and Ungors will all hit other Ungors.