Spotting units

[Montana Grizz]

This happens all the time to me:

I attempt to move a unit into a hex and all-of-a-sudden an enemy unit(s) appears in that hex.

I am assuming that that unit(s) had Op fire set to "never" fire on the type of unit I am moving.

My question is: If I had left my unit next to the enemy, not knowing he was in the adjacent hex, would the enemy spot my unit despite the fact that I did not spot his?

I am under the impression that both fire and movement within view of the opposition gives that unit away in terms of visibility.

Another question: If I set Op fire to "never" verus any unit and then use direct fire and destroy the enemy, will my unit still remain hidden from the next enemy unit that occupies the hex the destroyed unit once occupied?

Thank you,

Pat