"We will watch a Korean movie on the weekend."
I also didn't put 会 & got it wrong. Is it actually needed (vs just not added yet as a correct answer), and if so is it because we didn't specify which weekend?
Like. You don't really need the 会 if you say "NEXT weekend we'll watch a Korean movie," but this example just said "weekend". So maybe it's for clarity? "[On the] weekend, we WILL watch a Korean movie?" I still think it should be ok without it though, because if it meant a past weekend we'd use 了 to mark it perfected.
Also correct. I believe that developer only considers the literal translation.
It is common for one to treat 這個 as "the", even if it literally means "this one". IN reverse course, such answer is also accepted.
In this case, your translation (time-subject, subject-time; vice versa) is good to go for.