I've moved your questions away from the Regent guide into the Scions Handbook, since they're not relevant for the domain level of play - but are relevant for the creation of your character.
And to all who're interested in fleshing out their characters; I would wait untill Bjørn uploads either the old or a new character creation rulebook, there are many more topics to consider than just the few I answer below.
Well, I fear that not making a full Pc sheet for a PC is impossible for me - I make Cs I'll never play as a hobby from time to time... apologies for asking a question irrelevant to most but:
Q1. Are the 4 listed domain levels skills (Administration, Command, Spellcraft & Warcraft) class skills or cross-class skills - I can't see it in the regent's guide.
Q2. Is diplomacy also be a domain level skill? Or is the area covered by administration at domain level?
Q3. How many feats does it take to cast domain spells? I think someone mentioned 3...
Q4. How many feats does it take to be a scion? Robert's PC sheet suggested 1.
Q5. Does being a scion wipe out the human +1 skill point per level?
Q1 According to the old rules (that may change - Bjørn, an update in the Scion's Handbook section of the forum maybe?), this is the list:
Administration (Int; Trained Only) [Class Skill: Cleric, Guilder, Magician, Noble, Rogue] –
Allows a character to cut domain costs.
Command (Cha) [Class Skill: Barbarian, Fighter, Noble, Paladin, Scout] – Allows a character
to improve the abilities of units he commands during the battle stage.
Warcraft (Wis) [Class Skill: Barbarian, Fighter, Noble, Paladin, Scout] – Allows a character
to act well within the framework of the campaign stage.
Q2 My old character had a total diplomacy skill of around twenty and made quite a few sweet deals all over the place, with enemies and allies alike. I would say the diplomacy skill has a huge effect on all things. But then as now, the diplomacy skill doesn't have any visible effect on the rules.
Administration has nothing to do with diplomacy.
Q3 The old rules state the following:
Realm magic Prerequisite: True magic/divinely gifted, Scion, Cast Ritual Spell, Cast Realm Spell, Extend Spell or Enlarge Spell, Empower Spell or Maximize Spell feat, Ritual Casting: 8 ranks.
Q4 Scion is a feat.
Q5 No