EC2 yes, Lambda will not work with Strapi due to the nature of how Strapi functions and the cold boot time. Many have tried over the years to get it to work without success and it’s not an environment we are likely ever to support.
Generally yes but the user never sees that in many cases were you are using a SSG or SSR in which the server is requesting the information from EC2 at build time while still supporting other UIs that aren’t SSR/SSG.
Really depends on the use-case, I’ve also seen instances were you don’t host Strapi and just run it locally to update content then trigger a rebuild and push that to your static hosting (frontend).