In many cases you could want to install the phpBB SEO premod on a pre-existing phpBB install (eg keep the db, user, posts et all). This is always doable, but there are many cases.
Let's start with the the simplest case :
- phpBB vanilla (no modification what so ever) to phpBB SEO premod same version
Here we'll assume that we are talking about the latest version (for both phpBB and the premod) since there would be no point to do it on an outdated version (we'll talk about updating phpBB and ...