Two lines in two intersecting planes can be parallel, intersecting, or skew.
A line, or intersecting planes.
A dihedral angle is the angle between two intersecting planes.
Two walls or a wall and floor of a room intersecting.
A line. Unless the two planes are the same, in that case a plane.
Yes, two planes have intersected.
Not really. A railroad intersection would be an example of two lines intersecting. An example of two planes intersecting would be the ground and the side of a building or the ground and the railroad crossing sign post.