What can the LCI (liquid contact indicator) tell you? So the iPhone official website states 


"An LCI will activate when it contacts water or a liquid containing water. The indicator's color is normally white or silver, but when it contacts water or a liquid containing water, it will turn fully red. An LCI won't activate because of humidity and temperature changes that are within the product's environmental requirements."


I also know that 


Once the LCI changes color it does not come back; i.e. it's permanent


Can it tell you whether(=can you infer from the two statements above whether it is true that)


If no amount of moisture was present during the history of its use, to light the LCI, then no moisture was present to seep into the iPhone and damage it. 
If no amount of moisture was present during the history of its use, to light the LCI, then no moisture was present to seep into the iPhone and expose the user to non-charging electrocution risk* (unless of course your hands are wet again)


non-charging electrocution risk = electrocution risk while not having the iPhone charged.
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.