AEM react SSR adobe IO

hi,

I don't have react knowledge but I'm trying to understand few things, I was reading few AEM articles on React integration and I'm still not clear on :

1. Is it possible to create AEM React component that can be drag&drop to the page as regular AEM cmpnt ?

2. I'm not clear why do I need to change the page so that header/footer are also react components ?

3. What I need is to create one React app and to use it as regular AEM cmpnt (that has cq dialog, etc...) on regular AEM page.

4. Since I need to use server side rendering with Adobe io, can I still achieve #3 ?