The mages guild in skingrad
Yes
oblivion would be better because of the graphic i played fable when i was little im like 12 now i turly think oblivion better because u can cheat more on it the fable and the story line is more creative like the drak bro hood and figherters guild mages guild or thifes guild so i give fable a 6/10 and oblivion 9/10
You have to become a member of the mages guild. For you to do that You MUST do a series of misions.
You can buy it at Anvil's Mage Guild.
In Oblivion yes it is a mod. In morrowind it is the bloodmoon expansion. In Skyrim its part of the fighters guild (companions) storyline
Thieves Guild missions.
Yes, in "The Elder Scrolls IV: Oblivion," you can recruit a partner for your character in the Fighters Guild. You can hire a mercenary from the guild after completing certain quests, such as "The Blood of the Divines." Additionally, you can also recruit specific NPCs, like the fighter named "Grommok" from the guild. Just ensure you have enough gold to pay for their services.
Not 100% sure about general merchants but I know that all Thieves Guild members sell them. Just join the thieves guild.
No, you can kill people freely at other times, just as long as they are not also part of the Thieves Guild faction.
In order to gain access in the Arcane University, you must first join the Mage's Guild and gain the recommendation of each of the guild's representatives. Here's a good walk-through for the Mage's Guild, if you're interested: http://www.gamebanshee.com/oblivion/magesguildquests.php
every city but kvatch and the imperial city in the imperial city is the univirsity
They are in all of the cities mages guild mostly or in the ARCANE UNIVERSITY.