Yes, oboe is responsible for tuning the orchestra.
an A 440Hz, in an orchestra given by an oboe
It depends on the orchestra. In the U.S. in symphony orchestras, it's normally the oboe.
The Violin, Viola, Cello, and Bass all have "A" strings, so picking the note "A" as the tuning note allows all of the string instruments in the orchestra to have a common reference point. The violin and bass do not have a "C" string.
I believe there is no word for it, they just tune up. Usually the first chair first violinist, the concert master, will come onto the stage after the orchestra is already seated and the concert master will play an A usually and then the orchestra will tune.
A standard symphony orchestra can tune to three different members: the principal oboe, the concertmaster, or the solo pianist. The oboist is used to tune whenever there is an oboe in the orchestra, the concertmaster is used whenever there isn't an oboe, and the pianist/keyboardist will play the tuning note if he or she is the soloist for the evening.
Currently in America it is set at A=440, however, some European orchestra like to go a little higher anywhere from 442-5 but in music history A has ranged anywhere from 425-460 if not a wider range of variance
King David decided that the men of the tribe of Levi should be responsible for the music of the divine services: therefore, they were an "orchestra".
The most interesting role the oboe has in an orchestra is tuning. The oboe is the hardest instrument to tune and with it's piercing sound, it's ideal to tune to rest of the orchestra. The oboe often plays a solo role, it's capable of playing softly and sweetly on one hand, and on the other it can be piercing and harsh.
Orchestras are usually tuned to an oboe. The open note, (that is, the note an oboe plays without any fingering), is an A, and the orchestra tunes best to that note. When a piano is featured as solo instrument, the orchestra tunes to the A of the piano, because it's easier for them to adjust their pitch than for the piano.