Sorry, but what is the difference between ledig and fri exactly?
It's a bit like the difference between being free from work and being available.
I just got out of prison. "Jag är fri i dag."
I find it interesting that ledig in German means single, as in having no boyfriend/girlfriend. That's also a kind of freedom
Why is it spelled "I dag", "I morgon" and "I går" on Duolingo?
In the lessons I've read from other sites, and everywhere I've seen Swedish people write, they're written "Idag", "Imorgon" and "Igår".
Both are perfectly ok and should be accepted everywhere, but i dag, i går etc are recommended by the Language council and others.
In dutch, ledig means empty (old word) and is sometimes used as 'having an empty/lazy day or existence' (ledigheid). So free, single, empty - nice array of related meanings for ledig :D