An often mistaken fact is that the Number 2 engine exists on only multi-engine types. All aircraft, up to 5 engines, require a Number 2 engine for CASA compliance. Non aviation types will think this is a joke when considered against a single engine aircraft however, that single engine is referred to as the Number 2 engine.
It all stems back to the Wright brothers and that famous quote; "Orville, that number 2 engine is playing up again!" This was reported at the time under the headline; "Seconds from Death!" Now, to the questions posed...
(1) National security forbids me from identifying what could be a target for terrorists however, if I was a terrorist, I'd aim for a more reliable engine than the Number 2. Not all engines are exposed at the front and the back
(2) The Thronomister has neither of these. However, it contains a rare substance known as Corbormite. This is extremely volatile but, LAME's are professionals & know what they are doing.
(3) Both. In tight situations, when stress is high & testosterone is flowing, you need a thronomister to handle the up and down motions on your joystick.
The engine numbers are random. Sometimes the Captain will be referring to the Number 1 engine and the Co Pilot will be thinking he is talking about Number 3. Whilst it can cause some CRM (that's Captains Random Motor) complications, the risk is mitigated by the fact that terrorists will have no idea which engine to target.