I am not sure. If you check the source they link in the Izzy repo it still says that they are looking for maintainers and there have been no commits in two weeks. So it is not quite there yet, but apparently they have solved the issue with the database not updating, and probably the app is usable by now.

It is great news that the Izzy repo is providing the app there.

It is not listed in F-Droid. Maybe they will do it in the future, that is currently the only issue on GitHub https://github.com/chenxiaolong/RSAF/issues/50. Until then, you could use Obtanium.

Check out this book: https://en.m.wikipedia.org/wiki/The_Knowledge:_How_to_Rebuild_Our_World_from_Scratch. It analyses that precise question in the first chapter. The author argues that even though Wikipedia is probably the closest thing there is, there is a clear lack of practical knowledge that will be essential in the situation that you are describing. Science progress heavily relies on industrial progress, and even if you know how to build something that doesn’t mean that you can do it, as there are other things that are required first.

True, but I would say that nube (cloud) is more common.

I am definetly not an expert, but it does look like Chamomile to me. A good test to make sure is to squeeze the flower between your fingers while you smell it. Chamomile has a very characteristic smell, and should be easy to recognise.