1) Is this any time a foot unit enters a building, wood or similar? They are immediately invisible, or it takes time to hide?Foot can hide in buildings, woods and some other terrain. They can only be seen by nearby enemy or if they shoot.
2) How near does the enemy have to be to see the unit in terrain? Let's say Example #1, a unit is hiding in the edge of a wood and the enemy is in an area of open terrain? In Example #2, both units are in a big wood.
3) Can non-foot units ever be hidden? Say, a cavalry unit is in a large wood. In Example #1, the observing enemy unit is on a flat surface and the cavalry is in the middle of the wood. Example #2 is the same, except the observing enemy unit is on an elevated hill giving a good view of the whole wood. Is the cavalry unit visible in both examples, or perhaps line of sight obscures the cavalry?