Do I think that you can acquire mastery from this course? Yes. In six months? Now that will depends on how much time you put into it - at 20 minutes a day, probably not. The more appropriate question would be can you acquire mastery from the materials in this course? I feel that you can if you take the time to learn the lessons and put in the practice time, there is no limit on what you can accomplish with this course.
If you have questions there is also a user's forum that seems to be fairly active as well as a 60 day no questions money back guarantee. I have included an intro video for stage five to get a feel for what you can learn. If you want to learn to play guitar or it has been years since you played and want a refresher course, then I highly recommend Doug Marks' Metal Method.