My guitar lessons are personalised to your own musical tastes & it is recommended to take weekly lessons for the best results.
This question is very much suited to you and how you learn. I do advise for younger students (age 8-11) that half hour lessons are sometimes better. Usually, students age 12 and up are more than capable of engaging for an hour. I often encourage students to try both, book an hour and a half hour lesson and see which feels best. It's your learning at your pace so pick the time slot that feels best to you.
Yes. Though from experience I find children younger than 8 tend to struggle with the guitar, so I recommend starting your kids off from 8 and up.
For the best results, I would recommend a guitar lesson at least once per week & is combined with plenty of practice in your own time.