asynchronous api call in Redux Reducer

I am new to React Redux exploring google docs while learning got the below doubts please clarify.

1. To call an asynchronous API which action needs to perform in the reducer

2. How to split data handling logic in stores (I believe using Reducer)

3. How the state is changed in Redux is it with the help of Reducers? or with the help of Actions My point is Reducers please correct me

4. const TodoContainer = connect(mapStateToProps, mapDispatchToProps) 
   (TodoWidgetDisplayComponent);
   
   export default TodoWidgetDisplayComponent
   

   what the above code do is assign manually or automatically to connect.

Additionally got some below mcq doubts:

1. if you render code at single page application then it may degrade your ranking in search engine indexing --- is the statement is true or false

My answer is true which will affect SEO please correct me

Thanks in Advance