What can the LCI (liquid contact indicator) tell you?
In regards to 3 - no, you cannot infer that because an LCI hasn't changed color, then liquid was never present in the phone. It just means that the LCI didn't come in contact with the liquid. Another part of the phone might have been in contact with water. Also in case of "moisture" then slight dampness in the air doesn't necessarily activate an LCI.

In regards to 4 -  again no, you cannot infer that. However, I must say that it sounds extremely, extremely unlikely that you could be electrocuted by a dry iPhone while not charging. I think you probably want to say more about why you're asking this question in the first place.