There was a bunch of questions coming in that I want to state here for others running into the same:
1. Allow to create quiz by user or editor/admin. Ability to set permission.
A: You can control this by the core permission who can create questions.
2. If user creates quiz then he is owner of quiz, others should be able to add new questions to that quiz and then those should go for quiz owner for approval. Once approved then it should be live.
A: Yes, each question goes into the moderation queue. This is implemented in the plugin.
3. Add quiz under category, upto 5/6 level category is enough.
A: Each quiz question gets one tag. The tags are the categories to choose from for playing.
4. Each user should have his score card. Knowledge skills board and points achieved.
A: There is a list for each user what he has played already. Also on the quiz starting page, it shows how many questions per topic (tag) have been played already. The built-in score system regards speed and correctness. Scores are only calculated by day. There is no monthly best, but daily best.
5. ability to view quiz only for registered users.
A: This you do with the core permissions under admin/permissions "Viewing question pages:"
6. Ability to select questions answer using checkbox (multiple options), radio button, or enter text in box.
Each question has only one correct answer. It is chosen by clicking on the big checkmark.
7. ability to add image to question.