Q: 1) What is the first 0 for "k 0 0"

A: 1) "k 0 0" Specifies the frame number and the value of the parameter. The first number is the frame number, this is always "0" for a static pose, an animated pose will have a range of numbers. The second number is the parameter value, for a morph channel it will be the same as the number which appears on the dial.

Q: 2) does "initValue 0" have to be the same value?

A: it does not need to be the same, but IMO it is often a good idea to set it to the same value. The "initValue" is the value that will be restored when you use one of the "Restore" commands from the Poser Edit menu. Using one of the "Memorize" commands sets the "initValue" to the current value of the channel.

Q: 3) I have pose files that have only the k 0 0 line for each rotate dial what effect would removing the other lines have?

A: If some  channel is set to a none-zero value, then "k 0 0" would set that channel back to zero. If you removed the k 0 0 the channel would remain at its present value.  It depends what you are trying to achieve with the pose. For example if the pose is supposed to change the head shape morphs then you want to zero any head shape morphs that do not contribute to the shape you want, but you may not want to zero the expression morphs. If the figure is smiling, you want it to continue smiling even after you change the head shape. Ideally normal joint rotation poses should not not change the x or  zTran of the figures hip. You may have positioned the figure where you want it in the scene, and you don't want it to jump to some other part of the scene when you apply the pose. The situation with yTran is different. The pose of the legs determines how far above the ground the hip needs to be, so it is usually a good idea to leave yTran for the hip in a pose file.