Level select
Load a game using the LR /skip<level number 1-11> command line parameter. Your game will begin at the matching level with the matching weapons.

Replace level 1
Load a game using the LR /lev levels\miss<mission number> command line parameter. The matching level will appear, with the default weapon and health, in place of level 1 when you start to play. The following values should be entered to start at the corresponding mission.