Hey & welcome!  Moe gave you excellent advice & I'm just going to second most of it.

"So I am going to start with Anders Level 1 Acoustic course here and I have some question even if the answers seem obvious."

You might consider starting at Fundamentals 1 or 2.  If you have any basic skills already, then you might be able to work through it pretty quickly a get a solid foundation or review.  And you might pick up a skill or idea that you have otherwise overlooked, but that will help you build that solid foundation you will need going forward.

"1st.  How long should I practice each lesson and how will I know if I am actually ready to move to the next lesson?"

You can consider yourself done with any lesson when you completely understand the idea and can confidently play the skills being taught.  That means you might have to keep reviewing and working on any given lesson for a while.  You can and should move forward in the course in the meantime to stay motivated & see what's ahead.  But keep reviewing & working on older material until you have it under your command.  Learning guitar is a constant process of refinement, of adding on layers of complexity to basic skills.

There is no substitute for hours of repetitious practice until the physical motions are completely second nature.  Make a regular practice schedule & stick to it.  Or go above & beyond it!

"2nd. I ultimately want to play Rock, Metal (Many different Flavors of Metal) and oddly enough I really like flamenco style guitar as well. so with the beginner lessons can I / should I also start doing the lessons in the specific genre I want to play at the same time or one thing at a time"

You can certainly have a look at the Rock course to see how your current skills line up.  In fact if your skills & understanding are beyond Fundamentals 1 & 2, then you should consider starting in the Rock course instead of the Acoustic course.  That's where you are going to learn to build the skills that will help with rock style music.

But you should be realistic about your skill level & your goals.

"(what is a good method) ?"

I'm not sure exactly what you mean here.  But in general, the best method is to follow a good curriculum, with a good teacher (so, Fundamentals or the Rock Style Course) & practice a lot.  Then practice more.  :)

Hope that helps.  Please ask more if necessary & best of success!