This (unfortunately) depends a lot on your genes. But once you do have these muscles there is something called 'muscle memory' that causes your muscles to come back way quicker when you try to reach your previous goal again. So keep going, it's worth it! Keep pushing yourself and give your muscles the time to recover.
While the visible changes might not be big at first, you are building muscle with every strength training rep you do! The tears in the muscle will repair with the proper nutrition and build. You'll probably notice a change in your routine before a change in the mirror.
Not sure, I guess longer than it takes to build fat right… I definitely have a lot of muscle. I just have a lot of fat over it. Sucks.
It’s depend on the frequency you making for the cardio or workout. The more frequent you exercise and do workout in a week, the faster it take to build muscle.
It differs between people, depending on gender, age, fitness level, etc. If a routine is kept results should be visible within 3 months