Day of 'Arafah

Assalamu alaikum.The Hadith in Muslim(Allah's mercy on him) Book 006 Number 2602 specifically states to fast on the day of Arafa,so that our sins are forgiven.Now Arafa day is only for those who stand in Arafa and there is no fast for them.It is for the rest of the Muslim world.So should not we fast on the day of Arafa as specifically stated in the Hadith?There is a Hadith which says about the Virtues of Dul Haj 9 but Prophet(peace and blessings of Allah be upon him)confirms in above Hadith it is day of Arafa.So how this problem be solved?Also can Eid prayer be prayed on Dul Haj 11 or 12?Is there proof in Fiqh?Was Salaam.