Im a Sorcerer with 18 Charisma so I gain Bonus spells per day for 2nd and 3rd LvL Spell.
If I up a Spell LvL1 with a Metamagic of +1 can I cast the Spell with extra gained "Slot" for 2nd LvL SPells per Day or do I have to wait till Lvl 4 where I first learn the "real" LvL 2 Spell?
The second. You don't get bonus slot of a given level before you're able to cast spells of that level.
Meta-magic feats require you to spend slots of a higher level than the spell you're modifying, so I don't understand how you think that would work.
Im a Sorcerer with 18 Charisma so I gain Bonus spells per day for 2nd and 3rd LvL Spell.
If I up a Spell LvL1 with a Metamagic of +1 can I cast the Spell with extra gained "Slot" for 2nd LvL SPells per Day or do I have to wait till Lvl 4 where I first learn the "real" LvL 2 Spell?
The FAQ would apply to all kinds of spellcasters, so...
I will point out that if you have a spell level entry of "0", this means you can still cast spells of that level normally, but you don't have any normal spell slots per day usable to do so.
Here's a relevant rules portion for Paladins, who have spell level entries listed as "0":
When Table: Paladin indicates that the paladin gets 0 spells per day of a given spell level, she gains only the bonus spells she would be entitled to based on her Charisma score for that spell level.