create challenge coding website like code wars

I have an approach for constructing a website like codewars.com or challenge coding. in addition, the programmers who want to make money as coding can be answering tests and get a dollar. so I have questions about this startup.

1. is possible that to using flask or Django frameworks to creating a challenging coding website?

2. which front-end web framework must be used in the project?

3. what can I do for improving the speed of a website like code wars?

4. What's your opinion about the securing?