Alright answer question time Woot 

1. You can call me LL or Luci XD

2. Humans are to not know about the supernatrual. Demons and Angels are not to show themselves as such its breaking their own rules .

3. Uriel relationship is mostly in heaven. he is loyal to god and the angels after his care. he is the older brother of Gabriel but he likes gabriel child like state. Uriel will be appointed a safety messure to the daughter of Lucifer when she gets to heaven by god.

4. Older brother, he is around five years older then gabriel.

5. I feel like your character would be with gabriel in all honesty. he would try to get him back to heaven and thats when he comes face to face with the daughter of Lucifer.