So far the things learned are.
1. The time in Camelot were the group is at are from after Lancelot was exiled.
2. The dark one dagger is actually the missing end of Excalibur.
3. From what we saw Emma is clearly not in love with Hook or else the kiss they shared in Episode 3 should have broke the curse like it almost did when Belle kissed Rumple the first time. So she may love Hook but she is not in love with him and is still in love with Neal/Baelfire.
4. As for the Brave front, Fergus died and Merida is older so maybe taking place anywhere from 6 to 10 years after her movie, and apparently the other clans didn't think her being a female could rule effectively and rebelled and kidnapped her brothers.