What is the difference between an Interface and an Abstract Class in C#?

Backend: String (mutable/imutable), Garbage Collector, using statement, out vs ref, async await, const vs readonly, middlewares, concurrent and parallel execution, DI and lifecycles, entity framework. Frontend: angular modules and components, state management, directives, interceptors, jwt Azure basic questions, my experience with azure.

1. About previous experience. 2. Explain one hook that is not default hook in React.