No, Kid Loki didn't kill Thor in the comics. Their relationship was complex but not to that extreme.
Yes, Thor did kill Thanos in some comic storylines.
Yes, in some comic storylines, Thor has killed Zeus.
Yes, Loki did kill Frigga in some comic storylines.
Yes, Loki did kill Odin in some comic storylines.
Yes, Thor has killed Thanos in some comic storylines.
There could be various interpretations in such a fic. One possibility is that it shows Loki's complex character development. His childhood abuse might have led to his feelings of inferiority and envy towards Thor. For example, it could be used to explain why he sometimes acts out in a negative way, as he is constantly trying to prove himself after such a traumatic childhood.
Yes, he does. Thor's kid in the comics is Torunn. This character brings new elements and challenges to the Thor universe.
No, Thor doesn't adopt a kid in the comics as far as I know.
In the comics, Loki's reincarnation as a kid happens through a complex magical ritual. But the specifics can vary depending on the storyline and writer's imagination.
Yes, Thor has killed Thanos in some comic storylines.