TI states that: The Trooper is completely immune to Traits that cause States, refer to causing Damage, or reduce the Attributes of the target. 1a) If someone tries to FO a model with TI, do they ignore that? Forward Observer says: The use of Forward Observer is a form of Attack with a BS Weapon that uses the WIP Attribute, and instead of forcing the target to make a Saving Roll, forces him to enter Targeted State. FO is also considered Non-Lethal, which TI also ignores. 1b) I assume you could still be targeted by the Spotlight program and enter the Targeted State that way? Underlining and bolding done by me. Question 2: If a unit with TI (let's say Karakuri) is in close proximity or engaged with an enemy unit, could you fire an E/M weapon (most likely an E/M grenade from a Domaru) at the opponent's unit? TI would completely ignore the effects of E/M.
Immunity (Total) will ignore Forward Observer, and E/M grenades for exactly the reasons you've identified. It will not ignore an E/M CCW though as they have Normal+E/M ammo, so the Normal part won't be ignored. Immunity (Total) doesn't work against comms attacks, so doesn't protect against a Jammer or Spotlight.
Question 2: I don’t see anything that would allow you to throw an E/M grenade where it would overlap a friendly karakuri. The basic requirement that templates do not touch friendly models is still there. Smoke explicitly allows you to break this rule; Immunity does not.
Immunity (Total) allows you to ignore not just ammo types but also weapon traits. How does this interact with impact templates? Does shooting a rocket at a Karakuri not produce the impact template at all?
The Trooper is completely immune to Traits that cause States, refer to causing Damage, or reduce the Attributes of the target. For example State: Dead, Continuous Damage, or ARM=0.