Oooh this one wont be easy, it seems like you are somewhat...missing the whole point?
(or I am missing yours
).
1) Ok, killing neutral ships is a bad bad thing, you will get penalized for that, sometimes it can even mean a mission failure, not to mention the poor helpless innocent /et cetera/ people there
2) NB stands for Narrow Band, it is a type of sonar that allows target classification by its sound profile (distinct frequencies the target emits).
3) What you mean by "lock on to target"? Actually, torpedoes, unlike AA missiles do not lock onto their target before they are fired. They are simply launched in the target's direction, and at some point (their enable range) they activate their sonars, seeking for targets...if they find something, they will go after it.