Two questions about building GHC from sources

I've got two questions about building: 1. If my bootstrap compiler changes (e.g., from 8.10.5 to 9.0.1), is Hadrian smart enough to rebuild everything? If not, how do I force it to start over? 2. At the moment I'm not installing my GHC; I'm using elements directly from the build tree. If I build GHC and then move the whole tree to the whole location, will everything be happy? Or do I need to do something? (Again, using Hadrian.) Norman