Hi you don't have to do the second though I would suggest that you do since it is more involved and will give you a better idea of how well you have the skill sets used learned. The first image is relatively simple and good for beginers. You will find a good percentage of the grays in the Naruto Manga are this level. But there are definatly much more complicated gray panels then even the second image in this tutorial.
As for how you did on the skills of doing the grays you did just fine. And since this tutorial is about doing the grays I'm not going to fail you on the other stuff that isn't as good as it should be. I will comment on them since they are a part of good cleaning and steps that are usually learned before learning the grays. The blacks are not all black and borders should be reframed. I see that you skipped training ground #1 1/2 this tutorial will teach you about reframing and getting the blacks good and black. As for this tutorial you pass.
It looks good. The grays are solid. A few of your lines get a little thin but not to bad. The main thing that you need to redo is the white lining around the sfx text. Those were outlined in white in the orginal and should still be outlined in white. Fix that and I can give you a pass on this one.