1. I dunno about what levels they're aquired, but I've noticed that even if you've reached that level, the quests don't become available until you're contacted via NPC linkpearl.

2. Regional, faction, Grand Company and Local Levequests use the same allowance (you get 4 every 12 hours, and can store up to 99).

3. Yes.

4. Yes. They spawn every 30 minutes.

5. You can start Grand Company quests at level 20 (the command center for each can be reached by going to the market wards and choosing them from the menu that pops up (maelstrom command in limsa, for instance). The quest chain to join the grand companies becomes available at level 25. Other than that there's sidequests all over the place..

6. The Lodestone has the best recipe guide. Check it out. I dunno much about crafting, 'cause it still doesn't interest me.