system
Given the following post, respond as if you're commenting on Reddit:
human
[Thor 2] Odin-Loki-Thor conversation and post credits scene.

If Loki disguised himself as Odin to talk to Thor then what happened to Odin? Is he aware that Loki alive, is he aware that Thor turned down  Asgardian throne? He would want to listen to Thor's reason. 

Is it possible that Loki disguise himself as Thor to have a conversetion with his father? If Odin alive then what will Loki do?

Second part of my questions concerns scene after credits. Lady Sif and Volstagg brought mini version of Aether in a container (just like Tesseract one) to a blond guy played by Benicio Del Toro and a hellboyish looking female apprentice. 

So what did actually happened there? I doubt that was sunctioned by neither Odin nor Thor. And that collector guy looked evil to me, smells like betrayal...
gpt
Benicio Del Toro was playing "The Collector," one of the "Elders of the Universe," the last remaining members of their otherwise extinct species who were the first to gain sentience after the Big Bang.  As their various races died out, Death herself gave immortality to the last remaining members.

These Elders basically need to have an obsession, otherwise living for billions of years will drain their sanity and their will to live.  While otherwise immortal, they will waste away and perish if they lose that will to live.  

The Collector's obsession, as you might guess from his name, is in collecting.  At first, he collected things because he had prophetic visions of great creatures who would threaten the universe.  Should any of those creatures succeed, he would be able to repopulate a new universe with the biological specimens he gathered, and then share the knowledge he had gathered as well.  That noble view has deteriorated after a few billion years, however, into an obsession with collecting all things rare and valuable.

This would explain his final statement: "One down, five to go."  What good is collecting one Infinity Gem if you don't go for the complete set?

If you wanted to keep something safe and away from others, the Collector would be a decent choice.  As one of the Elders, he has access to the Power Primordial, the remnants of the energy of the Big Bang.  Akin to the Cosmic Energy used by the Silver Surfer, it makes any Elder, the Collector included, a dreadful opponent.

Bear in mind that the information presented here is based on the Collector from Earth-616.  Earth-199999, the dimension of the cinematic universe, may alter this to some degree.