He had this expirience at the mountain. Pa and Ma frog also had chakra so he could practice.
....
Then he could recognize Ma and Pa`s chakra, because he was able to experience what they were like.
But when he was summoned to Konoha in sage mode by the frogs, he had never been in sage mode
in Konoha and getting to learn each person's chakra. How could he recognize Sakura's, Neiji's, Shikamaru's, etc, if he had never sensed them before?
In order to recognize a person you must first be introduced, so I guess you need to be "introduced" to someone's chakra in order to recognize it.
I can't understand somthing too. The vanishing which kakashi and loads of other charcters used...how can they do that? I mean if everyone can do it and its not a forbidden jutsu of some sort( obviously its not) then how come the ninjas just "poof" away when they have to escape or "poof" to any destenation point they have to go to?
They vanish because they are clones. When a clone releases the jutsu, they vanish and then the real ninja gets to know eveything the clone saw or heard. Kakashi usually makes use of a clone in order to check his oponent's abilities, and then real Kakashi comes into the fight.