They're trying to stick with one definition for each adverb. 'Seriously' is represented by another Korean adverb.
The hint said "That woman" or "The woman." It gave two possible answers but accepts only one. That requires explanation.
You are not wrong, but some KO-EN dictionaries translate beautiful as both 아름다운 and 예쁜, so we decided to accept beautiful.
How about the word 잘생겼다. Does it become 그 남자가 정말 잘생겼어요? I still haven't got the hang of transforming these words.
yep. for '마르다'(skinny), and '잘생기다', '말라요', and '잘생겨요' is wrong, and '말랐어요', and '잘생겼어요' is correct. Something about being understood as the condition(event) being finished, so uses '-었-' to express that it is affects the present.