Terrain Following in LAND mode

With Terrain Following disabled and no downward rangefinder installed let’s say I takeoff from the ground that is at 50m MSL to an altitude of 100m AGL (150m MSL) and then fly to an area of higher ground say 75m MSL and switch to LAND mode. My understanding is that the UAV will descend at a rate of 150 cm/sec (WPNAV_SPEED_DN) and since the higher ground is 25m above the home location it will not detect that its at 10m (LAND_ALT_LOW) to reduce its decent rate to 50 cm/s (LAND_SPEED) and so hit the ground at 150 cm/s.

If I set TERRAIN_ENABLE and TERRAIN_FOLLOWING both to 1 will it know that its landing on higher ground and switch to the lower descent rate at 10m above the ground ?

Does installing a range finder effectively override ArduCopter using the map elevation data ?. I read in another part of the forum that mixed mode of both a map elevation data and rangefinder terrain following is not implemented.

So if I install a rangefinder but it has a relative short range of say 3m so RNGFND_MAX_CM is at 300 will the descent rate change at 3m instead of 10m or not at all ?