These are questions no one can answer, no one knows. Those seem like questions that would be answered in a sequel but there's not one.

OK, let's go

1- Clearly red

2- all of Wenlock's spells were broken so he was back to normal

3- I don't think so...

4- she didn't age because she wasn't in human form, basically our body is like clothes, we have a blouse, if we wear it for many years it gets old and worn out, but if it's kept it will still look new, Brietta wasn't in human form so there would be no way for her to age, just like Daphne from winx club

5- At that time, people had children very early, so let's assume that the queen got pregnant at 20, then + 16 years of Brietta = 36 + 16 years of Annika = 52, counting + supposedly 2 years because a pregnancy lasts 9 months = 54 and the king is probably a few years older so let's assume 57. But that's just a guess

6- Wenlock only went after beautiful women and noble family, when he found out that the king and queen had another daughter, he went after again, wherever he had a beautiful woman he went after

7- good question, how are they 16 years apart, or was it 1 year later or the queen was already pregnant

8- probably yes, she married aidan and continued the lineage