1: Ulquiorra is intelligent. I believe he knew that in the final battle the stronger soul reapers would fight the stronger Espada Arrancars. That is why he didn't want to be higher ranked because then he'd have a lower chance of surviving.
2: Like I said before, Ulquiorra is smart so he is more likely to catch on to a second release/Bankai than others who ...
The Gotei 13 is a military organization in the Soul Society, together with the Kidō Corps and Onmitsukidō. They are not a private military organization, which is not loyal to one government, since they are loyal to the Soul Society.
If Gotei 13 is governmental authority, how can they exterminate Quincy if they act on behalf of Soul King? I don't quite ...
All the Quincies that were known of were wiped. It's kind of like in the book "The Knife of Never Letting Go", the humans think all the Spackle are wiped, but only the Mayor (in this case, Old Man Yama) knew that they were very much still alive. Hope this answers your question.
The tattoos are actually not related to the growth of Renji. They are mainly aesthetics, possibly done to make him look cool.
He probably descended from some family that has tattoos like his. Hoipe this answers your question.
The Gotei 13 was mainly used to keep the control and order in the Soul Society. They are also the first line of defense from any enemies, such as Hollows, Quincies, etc. They maintain the balance between the spirit world and the real world by eliminating Hollows, and guiding lost souls.
The main purpose of the 13 was to provide an authoritative sense. Hope ...
The blade of the zanpaku-to just channels the spirit of the users zanpuku-to. It was an incomplete manifestation of Zangetsu. So even if he had called Sode no Shiraiyuki, nothing would have happened.
Its like trying to call someone else's spirit (zanpaku-to), when you don't even own it.