line of sight on hill hex

Rule says: A unit on a lower level has line of sight onto the first hill hex and vice versa.
So, a unit on a hill only sees the closest lower hex and not the furthest ones?
So, a unit on a hill only sees the closest lower hex and not the furthest ones?

No, a unit on the first hill hex has LOS to lower hexes

generally, LOS is reciprocal, if the lower unit can see the higher unit, then the higher unit can also see the lower unit.
There is an instance where the higher unit can see over an adjacent lower friendly unit, but the lower unit cannot see the higher unit because of the intervening lower unit.