Hello,
Can’t respond to questions Q1 & Q3, since I used strapi with a frontend only once and I already had the frontend written in Angular so I just changed the API URLs and refactored the requests a bit.
Q2:
Mostly I use Strapi as middleware between two or more systems.
A real use case where strapi helps me: I have around 10 online shops (WP + Woo) and I’m using strapi as a single admin panel for all of them. First, I’m getting all the orders/products/categories/comments in a single place. When I modify some data in strapi all changes are reflected in my online shops instantly. I’m also using it to automatically import products/update prices & stocks from my providers on all the websites.