Ah..that makes my reply look rather silly doesn't it ?
Back to question one. Yes, the movement type is used for casualty table shifts. See the Cover state effects table on play-aid 8.
A mortar fires and gets a hit on the HPT. A BOT marker is placed. Resolving the combat no terrain shifts are used as these are done previously on the HPT yes ?
right, but the terrain may have "Cushion" effect, causing a 1L shift on the casualty table ( see 12.5.655 )
does the -3 DRM come into play on the initial combat or later attacks if the BOT marker and a target remain in the same position.
A BOT takes effect the moment it's placed. If a mortar with ROF 2 places a BOT on a target with the first shot, the -3 DRM applies to the next shot. Actually the mortar's remaining ROF would be doubles, so it would have two shots remaining, both with -3 DRM ( See 12.5.1126 BOT & ROF )
As long as the mortar has LOS to the target hex, all it's shots have a -3 DRM and it's ROF is doubled.
Remember that BOT's placed by mortars targets the hex, not the unit(s)( see 12.5.1122 , and can not be used to "follow" targets ( 14.6.4 ).
I hope that's a better answer