Hi Vishal,
Your question is rather broad and large, but fairly easy to answer. It's all possible with Mendix. I suggest you start building and gather people around you who have experience with Mendix. Some topics are basic knowledge, others require a lot more experience.
1. Just start building
2. arranged out-of-the-box by Mendix
3. arranged out-of-the-box by Mendix
4. https://www.mendix.com/evaluation-guide/enterprise-capabilities/identity-and-access-management-iam/