As we all know kakashi & obito uchiha were teammates when they were young. But what happened to obito?? is kakashi's sharingan eye really obito's??? and why did obito (or tobi) joinened akatsuki?????

Kakashi and obito were in same team when they were young.... there was a war going on in konaha.. and there was one girl in their team whom obito loved...she was kidnaped by the enemy.While trying to rescue her obito falls down and was sure he was going to die...Kakashi will be also fighting there...kakashi will rescue the girl .... then they will go to obito who was dying ....obito will say to the girl ( who is talented in healing technique) to remove his eyes and give it to kakashi ,because the enemy is strong ,and they both have to escape from there....
Im not sure that the one eyed akatsuki is tobi....

Ok, thanks but if the sharingan eye is obito's then how did kakashi managed to use mangekyou sharingan ? does it mean that obito learned mangekyou sharingan before the incident ????