The Game Menu

Game->Undo (U)
Undoes the result of the last arrow key or mouse action. (Clicking the right mouse button has the same effect.)
Game->Redo (R)
Undoes the last undo command.
Game->Restart level (< or Escape)
Go to the starting position for this level. (This does not discard the undo history, so it is the same as repeatedly using Undo, except that intermediate positions don't appear on the screen.)
Game->Replay (>)
This is the same as repeatedly using Redo, except that the whole sequence of moves is shown at the current animation speed.
Game->Save solutions->
By default, when a score is added to the score file, the solution is saved as well, for later review using the score window. This can lead to large score files, so this submenu lets you change this behavior.
Game->Save solutions->Always
Game->Save solutions->Never
Game->Save solutions->Ask
Self-explanatory.
Game->Scores (S)
Brings up the score window.
Game->Animation (A)
Set the time the robot pauses between moves resulting from a single action. This is not remembered when you quit CPSokoban; to set the pause to be used at startup, use Settings.
Game->Settings (Z)
Brings up the settings dialog, where you can set alternatives to the arrow keys and change which mouse button does what.

Undo normally undoes all moves resulting from a single action, such as a drag-and-drop. To undo a single move, type Control-U or hold down the control key while right-clicking. To redo a single move, type Control-R.