Although... Nationalsången says 'Du Gamla...', and technically that means 'Though Ancient...' either way.
It's because we have the phrase from the National anthem in the course, and the traditional translation for that is not literal (because it's a song). Anything that works in one place in the course can show up everywhere. But I'll see if I can change it somehow.
I thought you use gamla when it precedes the noun?
like in gamla stan or (possibly?) jag har gamla föräldrar
It's the same in both cases here, so your examples are correct.
But for singular definite words, there's a difference:
det gamla bordet 'the old table' but bordet är gammalt 'the table is old'
den gamla boken 'the old book' but boken är gammal 'the book is old'
One question: If gamla is the plural of gammal, then why is the national anthem "Du gamla, du fria" ?
See above, and "gamla" fits better with the rhythm of the song. Poetic freedom.